Comment by Macha

You need a banking app to use the bank's provided 2FA to log into the bank's website (no, they don't support TOTP or passkeys or other vendor-neutral solutions) if you want to do any online banking on your other devices.

You also need it to receive the PIN for the credit/debit/bank card that allows you to pay for things in stores, or to withdraw money from the ATM if you'd rather use cash.

If you'd like to send money to your friend, for example to split a bill or for any other reason, then you either need to do that in the app, or do it on the website but with 2FA on the app.

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This is the norm for all the banks here, citing PSD2 compliance. I'm sure it's not the only way they could have complied, but it's the lowest effort and banks are nothing if not conservative, so once one bank gets the OK for a given solution, they all follow suit.