What "serious" tasks does banking involve?

I log in to transfer money, to take a photo of a check to deposit it, to check my balance.

All of that is fine on a phone screen. Actually, it's a lot easier to take the check photo.

And a banking app is a whole lot more secure than a browser tab running extensions that might get hijacked, on a desktop OS whose architecture allows this like widespread disk access, keyloggers, etc.