I want to believe that the majority of coins that are held on exchanges are owned by day traders who have little choice but to keep their coins there, because of transaction speed and costs. Because it should be a common wisdom by now that coins held on exchanges are almost as good as gone in the long term.
I also want to believe that but i am not so sure how true it is. It is hard to believe but there are so many people who believe that some centralized exchanges are too big to fail, and so instead of being their own bank and keep their coins safe, they rather just let Binance do it for them, since 'it's too big to fail'. That's the idea many people have and that's why they lose their money whenever an exchange bites the dust.