I've said this before, but I don't think being responsible for your own security actually appeals to everyone, and that's fine.
Its probably a case of people underestimating their ability to keep 12-24 words safe and overestimating the security of their assets being in the hands of other people hiding behind opaque institutions. It doesnt appeal to everyone, but we should communicate clearly that it can be learned relatively easily by anyone, that none of the properties of Bitcoin apply to coins held on an exchange and what the consequences are of doing so. A newbie will thank you for holding them accountable if it saved them from being rekt. If i was a newbie i would be thankful if people annoyed me till i get the warning and then start to self-custody, instead of keeping a false sense of security and then getting rekt. Self-custody is the only way for Bitcoin to be different from the current system. A world with most Bitcoin held on exchanges wouldnt be so different from fiat. With encouragement, support and being annoying enough a lot is possible. I have never met a newbie yet that was unwilling or unable to self-custody with the right support around him or that lost anything while doing it.
Hence, why banks will likely always be used. Since, if you are someone that doesn't know anything about computers or security, trying to secure your life savings on a computer probably isn't the best idea.
A person shouldnt put their life savings into something they dont understand the basics of. Bank custody doesnt change that or makes this practice magically safe. Its the opposite, if theyre handing over their life savings to someone else and dont understand the thing its invested in, is even a worse idea. History proves this.