Why doesn’t Proton strongly encourage paying anonymously like some services and do they log more data than others? Is this concerning for you?

Even so. Defaults matter. Proton understands this. And there are many things they can easily do to make it harder for users to be identifiable without breaking any laws. You won’t have perfect anonymity, but you’ll be harder to identify.

Moreover, Proton can change their defaults. When you’re about to pay for a service, Proton can make it so that the first payment option presented to you, the one that is checked, is a gift card or cash, with a little note explaining why. It doesn’t hide or remove the option to pay directly with credit card. It just presents you with a default that is more private.

@NatureFriends make a valid point.

See the thread linked above for more suggestions.