Are they though?
I'm 38 and can't remember a situation in my life where a gun would have been useful. Not saying that I can't imagine such situations, I just find it a slightly weird example to make this point.
* defend myself
* rob you
* murder you very effectively
* enjoy target shooting
* hunt wild game
* provide peace of mind in troubled times when law and order break down
The fewer guns there are per capita, the more useful they become for criminals. They are so useful, in fact, that people will spend a lot of money and subject themselves to costly and invasive regulations just to buy one gun. If no one found them useful, no one would find it necessary to ban them.