First of all I would like to say that there are two types of crypto exchanges one is centralized exchanges and the other is decentralized exchanges. What you mentioned here means I can assume you are talking about using Centralize Exchange.
It's true that a big one like FTX whose incident has instilled fear in everyone about centralized exchangers.
However, I think the main reason people store their funds here is the trading and low trading fees, especially when a trader is actively trading while using other hardware wallets or offline, the trading fees are higher.  Moreover, other options are also available in centralized exchangers.  But for long-term holding, smart traders use offline.