They are actually really good kids, and sort of geniuses

When you think about it, Beavis and Butthead are actually pretty sophisticated for their age. Most teens I know are so dependent they'd probably die if they didn't have their parents looking after them. Most teens don't work, and most can barely make it to school each day. Meanwhile Beavis and Butthead both have jobs, both attend school full time. They pay their own bills, buy their own food, have their own home. They're doing better than most grown men actually.