>cards don't work perfectly as age verification either.

there are 0 "perfect" age verification systems.

plenty of minors can have their brother/sister/parents supply their id, or do the verification video. the on-device verification discord rolled out was, within hours, broken. i remember news reports of kids submitting photos of their dogs and being verified as of-age.

credit card solves most of the problem with much less downside than submitting my face (i am already okay putting my card info into most sites)

Prepaid cards can't masquerade as credit cards as there are easy ways to differentiate them (the numbers have meaning) and a minor getting access to the family credit card is the parents giving them permission. I'm not convinced credit card for age verification is a good solution for all cases but for cases where you've already used a credit card to access the service it would be perfect.