Small Nine year old, weighs almost 50 pounds, booster seat?

Okay, I have been reading some of the discussion boards on "How long to keep your child in a car/booster seat." Many mothers still have their child in a seat, due to their size, at the age of ten. My son is pretty short and weight almost 50 pounds, I must admit he hasn't been in a seat for a couple years now, at least. In fact if I tried to get him in a booster seat i'm afraid he'd be mortified. He's at that age where everything he does has to be "cool" and seem "grownup". Now I now this isn't an excuse and the consequences of not being in a seat would/ could far surpass the sillyness. But I can't help but think 9 is too old for a carseat! I mean, half our parents never even straped us in...and we were still here. Any opinions on this? When did you say goodbye to the booster seat?