Just because you support an alternative money system doesn't mean you have to be against the concept of a bank altogether. Bank exists because people suck at protecting their money. You don't keep cash in your house because you get breaked in. And same goes for crypto. You could get your key stolen. You could forget your passphrase. You could get hacked. And so on. Bank aren't invulnerable, but they sucks much less than average people at protecting their assets, and this is why people uses them.