Being an athlete is, for lack of a better word “Macho” in high school.
Singing for a man is considered effiminate and therfore not.
Boys don’t want to be “femme.” Remember the “Brady Bunch” episode where Peter was on both the Football team and in the Glee Club.
What do people say “Actors, oh they’re all gay.”
And it makes sense that gay people would go into acting. After all until very recently teens never came out. They spend the first 18 years of thier lives “pretending” to be straight to everyone.
So what is acting? Pretending. So it makes sense they’d be good at it, with all the real life practice they’ve had
So for boys,
Athlete = Macho
Singing/acting = Femme
For girls in HS they see athletics as for lack of a better word, “Butch” and “Dyke-ish”
Obviously these aren’t hard and fast rules, but overall general feelings
After adulthood, there are more actor/singer groupies simply because their are more ways to become famous via singing and acting then via sports.
Also remember you can teach an athlete to act. OK they won’t be brilliant but you can teach them to act acceptably, such as Michael Phelps on “Saturday Night Live,” or Alex Karras on “Webster.”
It’s not very likely you’d find many actors would could play pro or even semi-pro football, baseball, or basketball on an acceptable level.