Skid Mark did.
How you die does not redeem how you lived. - A black pastor on the life and death of Charlie Kirk

Doesn't he have sex with Julianne Moore in the movie?
My password is password.

It would have been cool to see Buck in some sort of clip, since Jack Horner claims that Buck is "one hell of an actor!", but I think we are supposed to infer that Buck's interest in Adult is specifically non-sex roles, while Maurice is more keen to be a performer (or how he says it, "The ultimate Latin Lover").
Buck and Maurice, also, do not have their main income being supplemented from the Adult, but rather from jobs outside of the industry. Maurice with his nightclub, and Buck seen working as a salesman (mediocre at best, however his acting has brought some nice p*ssy into the place we're told).
I guess it's possible Buck performed in hardcore, but I kinda get a sense that he was strictly partook in non-sex acting jobs whenever Jack provided them. While, Maurice, via a deleted scene, was given the opportunity to become a performer, belatedly during the early '80's, and couldn't perform. Effectively, ending his "Latin Lover" ambitions.