If you use a password manager (which they say they do) it's much quicker to just save that info and automatically populate it. Doubly so considering the MFA hell they went through.
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.
Still, PayPal is an absolute last resort for me.