Not since the '60s . . . the F-bomb was pretty rare in the sub-teen crowd in those days.
Never heard my son (now 27) say anything like the cussing in FO4 until his mid-teens (Who knows what he said on the school playground, though).
Don't get me wrong, I'm not objecting to the language and the mature themes in the game at all. In fact, I rather enjoy it. I'm just A little surprised that a parent of a pre-teen would tolerate it. Times change.
And y'all are right; it's none of my business, and I'm not telling anyone how to raise their children.
Dammit, there's kids on my lawn. I gotta go yell at 'em ...