Why exactly do you think(or not think) a post op trans person should disclose their previous gender prior to sex or any sort of dating?

Logically, if they are a woman, then they aren't a threat to their/your precious heterosexuality, which means that's not an issue. If it's a "they can't have children" issue, then should ciswomen who are sterile have to notify potential partners prior to dating/sex? If it's an honesty issue, then why don't you go tell everyone your life story prior to it.

So, I've never really gotten exactly why people hold this view that they should disclose, could someone enlighten me?