QR is not ideal but as long as Apple keeps such a tight leash on NFC payments, it's the only "open" option. It's ironic that by trying to keep NFC payments so secure, they've instead caused the wide proliferation of far less secure alternatives.

Physical card issuance is too high-friction for new entrants. It's much easier to attract new users with "just install our app" than "enter your home address and wait days for a card to arrive then put it in your wallet and remember to use it"