The other huge usability problem is the risk of getting hacked. Everybody, even programmers, didn't write 99+% of the code on the machines they are using. Even if you manage to go years and years without issue, that 1 time you get hacked and your coins get transferred out from under you will make you lose everything and there is no way to get it back. For normies, this is an even bigger issue.
This is no different from early currency -- it was very difficult to protect from theft, and when you had lots of it, you were an easy target.
I suspect how this will go down is the masses will use banks, who will offer cryptocurrency accounts with interest and insurance, while the savvy will continue to manage their own private keys.
