I keep seeing this where? What banks don’t allow you to go to their website and use them from your phone? Which government apps don’t also have websites?
Not in the western countries yet, I guess. I live in Thailand and have accounts in two banks and both of them only allow usage through an app that's only available through the App/Play store. Android version of Krungthai's bank app freaks out if you have developer settings enabled (even without changing anything, just enabling the access is enough to lock you out). And to use that app in the first place, you have to go to a branch and have staff set the app for, as passing the facial scan checks is impossible for foreigners.
Several German banks (at least mine, one of the bigger ones) exclusively have you use an app for 2FA, you can still log via the website if you are lucky (as long as you have that one saved) but not do any transactions. So I would call that required.
