For the value of crypto, and Bitcoin in particular, to increase in value substantially, it's almost necessary that banks become involved. Crypto right now is still not that easy to use.
If you lose your keys it's over. And that's a major problem.
For the people with a lot of money, they will want security for their crypto. Not just a hidden cold storage wallet in a safe or somewhere. They will want it insured and secure backups of keys and all sorts of things.
Also, people to manage their investments and buy when appropriate.
To reach a future where we don't need banks, it will have to get a lot easier to use, with more secure options.
Many of us seem to forget the extreme learning curve of crypto and the fear at various times of losing your keys.
The more options for people the better. There are risks and benefits for both self custody and using other services as well. One of the reasons I like Hive is that self custody is super easy and security is high. My long time wish was having an ability to store bitcoins and other coins within a Hive wallet. Now that would make self custody super easy for all.