It's not that difficult to get a non custodial wallet, write out your seedphrase and store them in a secure place is it? So why would you want to risk the safety of your funds in the hands of centralized platforms? Let's try to play safe at all time.
Yes, it's not difficult to choose wallets that we can safely keep our coins. And people are risking their funds in centralized platforms due to the convenience that it offers. When the time comes when Bitcoin's price increases and they don't have to deal with some network traffic if ever it will exist at that time and they're free to sell it on that point of time when it reaches the peak. I think that's one reason why many still keeps their crypto in the exchanges for quicker dumping purposes and they won't have to deal with any network problems and sudden increase in the transaction fees.