Same problem for marijuana companies.

The difference is that marijuana is illegal at the federal level while crypto is (nominally) legal.

It is not about legality. It is about the costs exceed the ability to make a profit, it all has to do with liquidity and capital requirements to mitigate the risks. If you want to blame anyone, blame all the scam artists and criminals that targeted crypto. The banks cannot profitable mitigate the risks. If a bank cannot make profits they will collapse.