why do you think we always will?
Discussion
reality > ideology
Because most people are not willing to learn new things. Can't blame them. They (we) were programmed this way to be dependant on government and financial system we live in and most people will always seek easier path. Self custody is far from being easy for someone completely new to Bitcoin. It's all too foreign to them.
With all tech that has features for users there are use cases, need states, personas that vary, and each use case and user work flow and need state will cause various usages. Among these, some are optimal with self custody, others need custodial neutrality, or multisig, or some other feature set. Custodial services are a component of an ecosystem. An ecosystem is what is materializing and evolving.