People relying on desktop and software wallets. Storing them in their computers and eventually losing access to them either due to hardware or software failures.
Not just software wallets, but also things like 2FA. Many people either don't have back ups for their 2FA, or back up to another electronic device (such as phone and laptop). As OP says, if both are stolen, you can lose access to all your trading accounts (and web wallets if you are silly enough to use them).
For 2FA, you have to have a strategy to securely store the backup of your 2FA as well cause you don't want that falling under the wrong hands either.