Its simple, if they don't do it what is right then they have to accept the loss happens in case of collapse or hack or rug pull.

It isn't a hard job to maintain a wallet so you can safely store your money, yes cryptocurrency is money just to remind if someone not aware of it.

For traders its inevitable to take all their funds off the exchange but they shouldn't hold their entire portfolio either, just only hold a part which is used normally for trading and move everything to a wallet it can be hardware wallet or simple one like Electrum.