Special laundry detergent for athletic gear?

I was at a specially running store a while back, and the staff and even other customers were touting this special laundry detergent designed for athletic gear. They had this whole spiel about how regular laundry detergent doesn’t “really” clean the synthetic fabrics that running clothes are made out of, etc. I didn’t bite, but I was curious.

My question is, if that was true, why isn’t Proctor and Gamble trying to sell me special detergent in the super-market? Lord knows they try sell me every other type of “special” detergent.