Tap to pay might seem convenient, but all modern bank Credit cards have wireless pay function, so instead of holding your phone against the machine, simply tap it with your bank card.
I personally have an iPad for banking and I have no need to have a banking app on my phone.
If people don't message me because they don't want to install Signal or send a SMS, I'm fine with that. Obviously what they want to tell me isn't important, otherwise they would take actions.
Shops that can't give out exact change aren't trustworthy, so I shop elsewhere. If you run a business and accept cash, you need change money. If they can't or don't want to work correctly, I will not buy or only in an emergency once and then never ever again.