What's stopping Mercury or Brex's partner bank from pulling the carpet out from under them too? The bank I switched away from to join Azlo is archaic and frustr

What's stopping Mercury or Brex's partner bank from pulling the carpet out from under them too? The bank I switched away from to join Azlo is archaic and frustrating to deal with but I'm having second thoughts creating an account with another banking startup if it might close a few years later. I now have to inconvenience my clients and ask them to update the ACH information they have on file. I have no idea if there will be problems getting my money out either. I never expected this from a bank.