Controlling your own crypto keys is like having your net worth in cash or gold stored in your house. It could easily be lost or stolen or destroyed in a fire unless you take extraordinary precautions and then it is all gone.
It's not at all like storing gold, since you can have multisig wallets. You can make it arbitrarily difficult to lose or get stolen, depending on how thinly you want to slice your secrets and how many friends you have.
It's not an enormous error prone hassle there are third parties that make it pretty intuitive. Just because you don't know how to do something doesn't mean it is impossible.
Can you really imagine the average person ever doing this? Or even understanding how multisig actually works? When you need to start engraving wallet addresses in titanium you have to step back and ask about usability.
