Why are third trimester abortions controversial?

[Fmr. Gov. NickG]

No one except extreme pro life activists and concern trolls ever brings up "late term abortions"--they're rare and, in many cases, medically necessary. Pete Buttigieg of all people actually nailed this argument on Fox News of all places:

Well my point is that they shouldn’t be rare. Women are conditioned to believe their freedom ends even in the bluest of states when you hit that 6 month mark. That’s obscene.

Even if the "rights" of the fetus were not a factor, why would a woman who knows she wants an abortion wait around until she's 7-8 months pregnant?

There are circumstances where there might be good reason for this (e.g. detecting birth defects), but these will always be rare.