Mathletes are nice to have around the house
Also, depending on the HS, sometimes even "cool" activities aren't that cool...i.e. if everyone who went to Hamburger HS who tried out for cheerleader got to be one, that kind of cuts down on the coolness factor.
Don't worry about it. As you said, if a group is so homogenous that it only wants pageant queens or majorettes, you probably would not enjoy membership in it anyway.