This isn't about the bank's security - it is about the users'.
Users are losing billions worldwide due to fraudulent apps. If a user has root and runs a malicious app, it can intercept what a legitimate banking app does. A scam app with root can draw over the screen and tell users to transfer money, or it can run a series of actions when the banking app is running, or do any of a hundred things to steal money.
Users are losing billions worldwide due to fraudulent apps. If a user has root and runs a malicious app, it can intercept what a legitimate banking app does. A scam app with root can draw over the screen and tell users to transfer money, or it can run a series of actions when the banking app is running, or do any of a hundred things to steal money.