I'm surprised the play here is to make your own bank rather than integrate existing banks. I've never worked in finance though, maybe integrating with banks is a PITA.
The business models here is to be a bank that raffles money based on your deposits. And they need to hold that money to generate the profits to support those payouts.
It's quite clever. This fully disrupts businesses like scratch tickets which are quite popular (haven't seen one gas station that doesn't sell them).
I actually wish I had this idea. It's super smart. My only doubt is that this model apparently doesn't scale just with holding money. Digit tried that for a while and then they start charging for their sevice.