Because smaller banks don't have the compliance team or technology to allow other companies to manage accounts. There's only a few banks that do this. All the

Because smaller banks don't have the compliance team or technology to allow other companies to manage accounts. There's only a few banks that do this. All the challenger banks mainly use the same banks. The core bank systems don't support multi-tenant, most were designed in 90s or 80s and sometimes 70s. The bank needs to build a middle tier to control access so accounts are separated between companies. Protocols to these systems are terrible, its pretty much a terminal and you are reading columns and line positions to get data. SVB i think actually runs a pretty modern core bank system that has "modern" API, probably soap.