Slavery and servitude were part of life for thousands of years, since the dawn of civilization, and dying to escape it was certainly unappealing to most people. Spartacus marched those men as if they were pigs to a slaughter, which is drastically different from simply being given a choice between slavery and freedom. Also, not all slaves would have been as fit to fight or as courageous or suicidal, and many would have been content, or at least complacent as you mentioned. In the end, it was free men who died by the hundreds of thousands to end slavery.

We aren't free in many ways, but I think much of history has demonstrated that a willingness toward servitude is where most people feel safe. An exercise of willingness under social pressure is mistaken for freedom. Freedom is also an illusion of equality of opportunity, which is relatively fair.

I don't think freedom is possible, but if it was, I don't think anyone would want to see how it compares to willing servitude in hindsight.