Too many sites have broken forms. Sure, you can have the card autofilled but maybe it doesn't trigger the autofill for the address or maybe that wasn't even loaded yet. Maybe you can just click there and have it auto-fill but they can be so broken it doesn't autofill completely or fills wrong. Some sites are smart enough to have a checkbox for "shipping address is the same as billing" and others aren't.

When you use a 3rd party payment provider like PayPal it does a really good job of forcing all of this to be automatic compared to things trying to autofill custom forms just because it's integrated by the site instead of the user. MFA hell is starting to erode that actually being easier though and now there is more and more often no simple approach left.