There are 8 billion people on Earth.
It takes 4.5 years to complete 1 billion transactions on the blockchain.
Most of the world can never self custody.
What does that mean for us that do?
Discussion
Self custody is not the purpose of Bitcoin - the purpose is to fix the money, so no one can fuck all humanity and capture it by controlling money.
People having accounts in custody is not a big deal, so be it.
I thought the entire point of bitcoin was to remove trusted third parties. The money is fixed by capping the supply, a fair and equitable issuance, and self custody.
I see it similar to "not everyone will run an email server, but everyone has the possibility."
In most cases, people don't want to be responsible for much. It's a hassle.
We help them
I think it realistically means that not everyone will have a UTXO, not that everyone can't self-custody.
Most people will ideally be in some n-of-n multi-sig arrangement with layers of peoples they can choose from to cooperate with while still being sovereign enough to be able to change groups or exit entirely when those peoples become less than cooperative.
For money to be useful it needs to be accepted by other people anyway, so the cooperation (but not the trust) of other people I think is a reasonable scaling solution.