Challenger banks who launched thinking this often end up owned by or serviced by traditional banks. Some of that thinking is at least making its way into traditional banking, but it's a slow process with entrenched interests fighting every step of the way.
I had always heard the problem wasn't necessarily the knowledge, it's more that starting a bank from zero in the US is extremely labour-intensive; something about having to get licensed by every state with its own slightly different set of rules.
The SOP seems to be to find some dinky bank with an established license and acquire it to get a seat at the big-boy table. I suppose, then, it inevitably leads to a culture clash as the "Bank people" can say to the "Tech people" that the moment they stop playing ball, the whole thing crashes down.
