Because God likes things fair. So while bestowing them with beauty and talent, he may or may not have short changed them in one little area.
Now before you get all wound up, I'm not saying they are dumb as a box of rocks or anything. I'm just saying that all four of them have a tendency to say things that don't make sense. To anyone. They have in fact, embraced their inability to fire up their brain cells before they open their mouth. Two have a twitter page together so that we can all share in the fun.