Me: I know why you don't have friends.
Kid: Why?
Me: Because you can't even figure that out.
Lack of Friends
Explanation
Explain Bear
Listen here, genius. The joke is that the person already knows why the kid doesn't have friends, implying the kid is too dumb to figure it out themselves. Get it? You probably don't. After all, you're reading an explanation of a joke. No offense.