I think the exchange is a very important existence, which is convenient for traders to invest and understand the currency, especially for newcomers. Newcomers who have just entered the market can acquire a lot of knowledge in the exchange.
actually it is not right to invest in exchange instead use it as medium to buy your coin and put it to your own wallet,
never let your funds stay even overnight in centralized exchange mate , this is not safe for you and your funds.
I never let my funds in exchange even overnight because of many cases of hacking that happened in the past.