Because those well known names would probably distract from the storyline. Start mentioning the DeMeo crew and the Westies and the audience might expect a bloodbath. Keeping with the concept of the show, the adult entertainment industry in the 70s, it's probably better to emphasize the mob's role as business people in this story, and minimize their dialogue. Honestly, I think having any mob characters above Michael Rispoli's character is kind of overdoing it. Reeks of wannabe Sopranos stuff. Should have just done it like Mean Streets, especially since it takes place in that same era. Have one important mob guy, maybe a couple of his goons, and that's all anyone needs to know.