The reason why it's hard to become a bank in the US is because there are regulations in place to keep companies from screwing over customers for their own gain

The reason why it's hard to become a bank in the US is because there are regulations in place to keep companies from screwing over customers for their own gain or in their own stupidity. In this case, Robinhood didn't look into what they needed to do to follow those regulations. If they DID follow the regulations, then they could provide their banking service.