I understand why some people are preferred to keep their Bitcoins in an exchange wallet and that is for trading, not for holding. But these people know what will happen when an exchange got scammed or whatever, yet they still do it despite the risk because of their trust. It could be a manipulating power that most exchanges injected into the mind of the holders. We know it was wrong but can't change their stances as well as it was their choice. They will change their minds when experiencing losses of their funds from exchanges.
And what kind of way out do you offer for those who are engaged in everyday trading and who need to have constant access to the exchange? Cold wallets are, of course, more reliable and safe, but you can’t really trade with them. With the cold wallets the exchange rate update is late, and the commission is higher, and transactions are not completed so quickly. The exchange is more convenient for trading, no doubt.