It should be taken into account that some whales are certainly not confident enough to keep their coins themselves, so it makes more sense for them to leave it to professionals, no matter how wrong it actually is.
I don't know if it's true that they cannot rely on themself but they rely on some services like exchanges. I am sure they don't know about the bad side of it. I know one story that I can share with you. I have a friend who lives in arab country at this moment. But, he opened his account on Coinbase when he was in Bangladesh. He had some Bitcoin in his Coinbase account, and he planned to hold it for a long time. I didn't say anything because he does not understand much. He might lose his seed phrases if he uses a non-custodial wallet. So, I let him use Coinbase because it will be easier for him to recover the password and access the fund again.
But, a couple of months ago, coinbase started to send emails to Bangladeshi users that they were going to close some accounts, I don't know if they closed all the accounts, but my friend received an email too and he didn't even read that. Just because I knew that he used coinbase, I asked him if he had received any email. He asked me to check for himself and yes, he received it too. Luckily, I assisted him in moving his funds.
So, I have a feeling that a lot of wales are in danger without knowing that centralized exchanges can take any action whenever they want and you have nothing to do when your fund get stuck.