By allowing people to shoot themselves in the foot after ignoring a unmistakable warning, you are helping teach the foolish to be more careful in the future. Making mistakes is the best way to learn something.
If they even notice, that is. It's just as possible that they play open relay for a year before they move to a new phone because their battery is always dying so fast for some unknown reason.
What reason do you have to believe that this goal wasn't achieved?
Plus, you are not required to do that, you can just stick to Google Play and trust what Google approves there. But no need to lock down others because of your recklessness.
Why the hell can't I use my rooted device for payments? It's my goddamn money at risk.
Plus the whole "banks need to protect you by ensuring your device" is stupid when cards are protected only by a PIN, and the app also requires some form of biometry to unlock it, which is to encrypt the underlying tokens. Banks should protect your money on their end, with clients having their responsibility to keep safe their stuff, whether that's their card or phone. It's a stupid premise itself, and it's lazy engineering.