The funny ( ok it is not that funny ) thing is they use cryptos in the same way they use banks. What is the point of using cryptos if you put all your Bitcoin/Ethereum/Monero/Litecoin/etc... in a web wallet?
Even if you don't use them as a "web wallet", you can still get bit when you go to exchange and find out the exchange is not trustworthy too late and your coins are gone. Many defunct exchanges continued to allow deposits while blocking or limiting withdrawals.
The popularity of exchanges points to a fundamental mismatch between the values of bitcoin and those of the general population. Most people don’t really want trustless consensus, to be in charge of their own security, and pseudo anonymous payments.