When I mentioned a laser focused niche, I meant that by being niche focused (like Venmo or Paypal) you can avoid a lot of the overhead needed for having a wider selection of banking services. The common example here is no physical locations, no tellers, less overhead. But it also applies that if you don't do mortgage lending you don't need mortgage specialists and you have less interest rate risk to manage

[edit] re: ldayley comment, I'm referring to vertical niches of service rather than horizontal market niches