Why do people disagree to the fact that there can't be a geeky athlete?

in my school, we have 3 seasons of different sports venues. season 1 (volleyball, X country soccer) season 2 (Swimming, Tennis, Rugby, basketball) season 3 (Softball, badminton, track). after varsity, each team picks the top athletes in the team and they go on a sports exchange to IASAS schools. i am one of the top swimmers in my school, but i am a geek. whenever i tell people that i'm a swimmer, they laugh and say "You? no way". why can't people accept geeky athletes?