Rocks in tire treads

I always pick my rocks out of the tire tread! I use a old phillips screwdriver and ground the end of the screwdriver to resemble an ice pick. The rocks come right out! If you don't remove the rocks they will come out sometime while you are driving. If you have mud flaps that will stop them from hitting someone else's car from behind. What most people don't think about is they can fly out in the forward position and hit a vehicle coming at you in the opposite direction. Good Question!