Some banks, especially newer ones, don't even have a browser version. Or they do, but they require you to use the app for 2FA.

When the app itself is also the second factor.

You don't get payment notifications when you use the browser version and you can't log in with a fingerprint scanner.

I don't need payment notifications (I check it regularly anyways) and I actively don't want to use biometrics for logins, so there's 0 loss for me.