Because they believe (or pretend to for political benefit) that you “kill” the fertilized embryos that you don’t use. IIRC this is one of the Catholic things that migrated into Evangelical Christianity when they started to make abortion one of their major issues.

Catholics have always been against abortion, IVF, birth control (including condoms), etc. It’s shitty but at least it’s consistent I guess, at least wrt abortion and IVF. The birth control thing is just stupid and the condom one is outright dangerous and criminal wrt STD’s.

Evangelicals just hopped on board in the past few decades when they realized they could use it to win elections. It’s really funny how they used to not give a shit about abortions, and they’re just now coming around to IVF. Thanks Jerry Falwell, you massive steaming pile of shit!