Muscles sell. We know this for a fact. A muscely actor with a good face is more attractive (to men AND women) than a slim actor with a good face. Muscles are advertised everywhere and usually generate great success for the product, e.g. a diet pill, fitness machine, or BBing/fitness magazine.
So, why are millions of men and women wanting to see muscles in a movie or magazine, yet not coming to shows to see it in real life? Niche sport - yes, but there is a REASON for that which must be known before its fanbase can grow.