Surely "Open the BankCo app on your phone and enter the code" is just as simple. For banks, for example, I already have a banking app on my phone (which was or

Surely "Open the BankCo app on your phone and enter the code" is just as simple. For banks, for example, I already have a banking app on my phone (which was originally authenticated via, ahem, SMS), so they could very easily put the OTP generator there.