I just don’t see a world where some form of custodial banking services doesn’t exist for the indefinite future.

Right, there will always be custodians. The point is it is a service not a requirement. Right now you cannot self custody cash at your house and spend that cash electronically with a card without being an accredited bank. With Bitcoin you can. But that same custodial service exists in Bitcoin. It just carries the same risk as a bank. Most people will trust a custodian and risk their asset for the privilege of not having to learn about wallet software and seed phrases.