I don't know how you came up with the knowledge that self custody is a bad idea.
Stories about people losing their life savings because they physically lost their Bitcoin.
Stories about people having their Bitcoin stolen from them at gunpoint.
Stories about people being tortured for their Bitcoin.
Stories about people being killed for their Bitcoin.
Stories about people seeing their loved ones killed for their Bitcoin.
Gee I wonder, how could somebody come up with such an idea?

If someone loses bitcoins in self-custody due to their own weakness or ignorance, [...]
So nobody is a victim of a crime unless they are weak or ignorant. Got it.
You better hope it never happens to you.

Since Bitcoin is the most volatile, insurance companies will not be interested in taking insurance against it, [...]
They would insure the Bitcoin, not the USD value of the Bitcoin. Duh.

Let me ask you, if a user who stored all his assets in Bitget, because according to you that self custody is bad, that people should embrace centralized storage. Lets assume the person got the news that Bitget has been hacked where he stored all his funds. Due to the news of the hack, he got shocked, slumped and died. Who do you think killed him? You dont necessarily need to shoot people with gun or torture them physically to kill them. You can kill people by your actions. So this your point does not in anyway justify centralized storage of assets.
Nobody is saying that established, well-known CEX's with insurance is some kind of magic solution that will make things "perfect". It's only that such a solution is far safer than the alternatives.
And for every anecdote about people losing money from CEX's, there are 1,000 examples of people losing money (or their life, or their limbs, or their loved ones) from self-custody.
(This conversation reminds me of conversing with people who won't get on an airplane because of a crash they see on TV, so they make a 1,000 mile drive instead, which is 100x more dangerous, statistically speaking).