Why does everyone think we're going out when we're NOT?

i just wore his jacket cuz i was cold. and its his letterman jacket so everyone knows who "he" is. im so tierd of telling ppl, im not going out with him, but no one believes me. we're JUST FRIENDS. and he gives me rides afterschool sometimes cuz he can drive and i cant. and we hang out a lot too, but thats cuz we're really really really good friends.