OTP using an app has a very low adoption rate. You'll be surprised that even on crypto exchange 90% of the users don't have access to any kind of 2FA let alone Apps. Only less than .1% of the users have an app installed. It's not convenient
This scheme also works really well with payments from your computer. Just use the bank app to scan a qr-code on checkout, verify the payment details on your phone, touch a button, and you're done.
I'd guess that a majority of the bank's clients are using this method. This is in the Netherlands, by the way.