On: Google seems to have signed me up for Google Pay without asking

[Mindwipe]

Yup.

Apple does the same thing.

[emeraldd → Mindwipe]

Last I checked, Apple is explicit in saying you must add a payment method to Apple Pay.

[messe → emeraldd]

Yep, I even need to confirm via my bank (online or app) to enable a card with Apple Pay (per-device as well, it's not just added to my Apple ID and then allowed everywhere).

I'm in the EU though, I'm not sure what it's like in the US.