It’s funny, I never knew of the formal philosophy of anti-natalsim (though, as a human, certainly familiar with the concept of never having existed). Yet, the very first thought experiment I had before deciding to have a child was to, in my head, have an answer for them if they ever asked me “why did you have me?” And make sure it was a really good answer.
I do doubt many folks do this but I’d be willing to bet most who have given any thought to their existence probably do.