Person isn't available to consent to thing -> people usually don't do thing in their stead

The situations where this is contradicted are only because there's a prior being extant whose interest is usually avoiding death because they find dying undesirable, whereas the unborn aren't afraid of continuing to be unborn and thus aren't harmed by inaction like a comatose person who might wake up some day might be.

A sleeping person exists, pretty big difference you're eliding. You're literally conflating being and nonbeing, which is, ontologically, just a wee bit confused. Anti-natalists never beating the allegations