The first big barrier is the registration and verification process. It requires us to spend some time, and then we still have to wait for verification. Sometimes even several days.
Secondly,the purchasing process itself is not the easiest one. If you are taking your first steps in the crypto world, it is hard to understand the rules of the order book and determine the price of your order.
Third, exchanges are systematically hacked. Or they themselves evaporate with our means. Keeping funds in the stock market is not safe.
An exchange that does not require verification. Well, it does not even require registration.