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.
Backing up money on electronic exchanges can be good but big crashes like MTGOX, BTC-E can happen even though we have found ways to bind many layers of security above.
Mobile storage forces people to update their software more frequently for both the phone and the wallet app. Older equipment may not be safe.
That crash at the exchanges is not something that we expect, and I guess people were not expecting it too. But that really happens, and people could only regret it without having a chance to get their money back.
If you store in the mobile storage, and you don't have to install too many apps. I think you don't have to update your mobile phone too often because if you just install the mobile phone wallet, the wallet developer itself will not release the update too often.