Not all people can afford buying a hardware wallet, but there is another option, non-custodial mobile wallets. So you don't have to keep coins on exchanges.
Using a non-custodial mobile wallet will be enough for them who can not buy a hardware wallet, and as long as they can know how to protect their wallet, their funds will not be in danger. But storing coins on the exchanges will give you risk from the hack or other things because the exchanges will not always secure. But if people still want to store their coins at the exchanges, they need to remember the risk and don't store in a big amount to prevent it.