Carrying a weapon outside of the home seems overkill because we have the police to maintain order.
Having a weapon inside of the home is impractical because it would mean carrying it around with me all the time, on the off chance that someone wants to break in while I'm in the house.
Likewise if I'm asleep and a noise wakes me, I'd still have to get to a gunsafe and get it open, then go looking for somebody in the dark who can clearly hear me thumping down the stairs.
I very much doubt I could pull the trigger and without a lot of training I doubt I could react in any sensible way.
I like the idea of having a gun, but if it meant that criminals were more likely to shoot me, or my mental neighbour could buy one then I'd rather go without.
What we should have in this country are licensed ranges where you can shoot an AR-15 for an hour, just to see what it is like. The police could run them to raise money or something.