You don’t just let them keep it all the time. You keep it locked up except for when they ask to see it. If you live in the absolute middle of nowhere on a large property then occasionally they may be able to go hunt squirrels/rabbits etc by themselves or target shoot at a home range but that depends on the kid.

I grew up with plenty of people who had “their own” guns at young ages but they didn’t just keep it all the time. Also legally it’s their parents just with the understanding that once they’re old enough it’s actually theirs.