I really don't see this as at all puzzling. If it ain't broke you don't fix it. If you're in a boat you don't need instructions on floating but on how to avoid not floating. You don't have emergency services on standby to rush to the aid of people who have nothing wrong with them. Harm, damage and pain are literally emergencies. How could they not be 'pressing'?

There have of course been attempts at what you would call a positive ethics, notably Utilitarianism, but they inevitably find themselves caught in the barbed wire of the realisation that it is rarely possible to promote pleasure or happiness to the primary aim at no cost in terms of harm to others. Increasing the sum total of happiness is an empty goal if the 'wealth' is not evenly distributed especially if some are actively deprived in achieving it.

It is no surprise at all that all the great ethical systems are prefaced on 'first do no harm'.

There have of course been attempts at what you would call a positive ethics, notably Utilitarianism, but they inevitably find themselves caught in the barbed wire of the realisation that it is rarely possible to promote pleasure or happiness to the primary aim at no cost in terms of harm to others. — Barry Etheridge

So this is exactly what I was talking about: the prioritization of harm. You haven't really done anything to explain why harm is more important than benefit, though, other than say that harm is an emergency, which begs the question as to why harm is an emergency.

So let's look at it from the other way round. I have a new ethical system X which has as its sole purpose an increase in pleasure and happiness. How might I achieve that if I do not first address those things which cause deprivation of pleasure and happiness? Even the most egocentric hedonism must address the problem of interruption to or deprivation of pleasure and happiness by others. In other words it requires rules that ensure that others cannot behave in a manner which negates benefit or, if they do, provides for 'compensation' to restore that benefit.

An ethical system which pretends to ignore or deprioritise the prevention of harm is simply empty. You don't fill a fish tank that's full. You don't charge a battery that's at 100% You don't provide a code of behaviour for those who do not, or rather cannot, do harm.

You could, of course, subvert this by claiming that pain is not real, that harm is illusion, that loss is delusion so that none of these is any true threat to happiness but I think we all know that not's true or, if it is, it's impossible to free ourselves from the illusion. Buddhists can preach the non-existence of pain all they want but I've yet to meet one that doesn't jump when you stick a pin in him!

Alternatively, you could claim that pain is real but it doesn't matter such is the importance of pleasure and happiness. You don't need an ethic which proscribes harm to others because it is the unavoidable consequence of seeking the true purpose of your own life. But it's easy to say that when it's not you doing the 'inevitable' suffering and hard to maintain when you've been locked up to protect the public from your sociopathic tendencies!

Even if we reduce it to the purely physiological, pain is something we are programmed to avoid, prevent, or relieve at the earliest possible opportunity. Moreover it is normative for human beings to be hurt by hurting others, to suffer for causing suffering. Anything purporting to be a recipe for the good life which fails to address these inescapable truths of the human condition is pie-in-the-sky idealism (with a small I, ie. the bad kind!) at best. At worst it's the kind of blind 'optimism' which informed the eugenics movement or the Aryan supremacism of Hitler! Nazism is the ultimate example of a 'positive' ethics!

So what I'm interested in exploring is why we see pain as more pressing than pleasure.

Because that's how your brain happens to be wired. Why are you expecting to find it based on logic in the first place?

It just happens to be a component of human psychology to look at things more in terms of danger and harm instead of pleasure and benefits. It's developed through evolution over time and is also called.............. the "survival instinct''.

This is a phenomenon that I've encountered in my own moral and ethical reasonings which I first became aware of through a maxim that I have never been able to actually disregard: "All moral dilemmas involve "harm" of some kind. If there is no harm, there is no dilemma". Also, I feel like I may have rambled, so TL;DR at bottom!

It seems true in every case that morality is only ever relevantly employed when a person or persons are confronting some kind of harm. "Moral justifications" always take the form of an argument for an action that itself causes some harm, (where usually the justification is the avoidance of greater harm). Moral arguments that appeal to harm instead of pleasure tend to make a good deal more sense because what humans on the whole deem to be harmful is a much narrower and consistent spectrum than is pleasure, and so humans agree much more often about what is "bad" (as opposed to agreement on what is "good"). It is not the case that "harm" is a universal value we can appeal to for moral argumentation, but it is a heck of a lot closer to being universal than is "pleasure".

Humans and groups of humans can much more easily come to agreements about certain states of affairs that are undesirable or "bad/harmful" than they can about which states of affairs are the "best/most beneficial". One way of looking at it is that certain moral arguments advocate for avoiding specific states of affairs that we all agree are bad (i.e: don't murder, don't torture, etc...) which amounts to a fairly simple active moral prescription; potentially all I need to do to avoid specific states of affairs is avoid a limited set of specific actions (i.e: murder) and the moral objective of avoiding specific states of affairs will have been satisfied. Moral arguments which instead advocate for reaching specific states of affairs that they argue are "good" (i.e: no starvation, no war, health-care for all) might entail a much more complex analysis of what actions or lack of actions might be required to reach the specific desired good state of affairs.

Avoiding specific states of affairs by predicting the outcome of our actions (or how we ought to make decisions on how to act) is a simpler empirical endeavor because we only need to ensure that our actions negate a specific set of states of affairs rather than negating all possible states of affairs but one. Even if we could all agree on the one "ultimately good" state of affairs that morally we all ought to work towards, we would still have unending disagreement about how to get there; more disagreement than we would have about how to not get to a very bad state of affairs.

Pain is not actually more pressing or important than pleasure in a broad sense, it's just that the moral arguments which ensue from examples of pain are much easier to wrap our heads around and are much more broadly appealing (widely agreed upon) and are therefore more commonly wielded. Given the more subjective nature of pleasure (compared to pain) individuals have a harder time trying to impose their own personal ideas about what is pleasurable and how we should be behaving (toward a "good" end) on others in the form of moral arguments. But if your personal idea of what is pleasurable, all the things you like to do and which makes life worth living, were suddenly taken away from you, I imagine that you would feel it a transgression against you with the same degree of moral gravity as you would if direct harm were inflicted upon you rather than just the removal of your available pleasures.

TL ;DR It's not that harm is a priority in life as opposed to pleasure, it's just that pleasure seems to be much more subjective. In addition, the moral prescriptions which follow from "what to work toward" ("good") rather than "what to avoid" ("bad") tend to be much more complicated affairs.

why, in ethical discourse, do we typically concern ourselves more with pain, suffering, or harms instead of pleasures, happiness, or benefits? — darthbarracuda

Who is "we"? What is the data set you're engaging with? You list four "principles," with three of them focused on harm, and comment on them as if they're THE four established principles. Where is that idea coming from?

Does it morally matter whether the rapist enjoys the rape, and weight it against the suffering of the victim? Is group rape morally better, because it increases the sum of pleasure/happiness of the group?

Try to solve this puzzle without equivocations.

Does it morally matter whether the rapist enjoys the rape — Emptyheady

I wouldn't be surprised if that mattered to the rapist's moral views.