Whole Body Gestational Donation The allegation is that surrogacy, while consensual, is exploitative. I don't fully subscribe to that logic because, like organ donation, it can significantly improve people's lives, including those who do the giving. But the risk of exploitation can still be there if women are poor.
I'm not talking about unsuspecting brain-dead women since we'd have an opt-out system in place for this similar to for organ donation. So, they could withdraw their consent to this while they were still alive.
But anyway, a brain-dead person, due to not being sentient any longer, no longer has any interests. Meanwhile, a sentient surrogate still does have interests, including the interest not to be exploited. So, the "injury" to the brain-dead person is less severe, so to speak.