It is important to remember that a response is not the same thing as a laugh. Audiences may initially laugh because they are shocked, but once the "I can't believe he just said that" wares off, it is up to the content of the material to do the work. If it is not clever, unique, or something different than basically just describing an awkward porno, then crowds everywhere will grow tired of your set fast. It is easy to go on stage and say whatever disgusting things make your friends laugh, but you cannot build a set based only on that. A purely sexual set may start off strong, but once a crowd figures out that dirty material is all that the comic has to offer, the laughs and attention quickly fade because nothing new is being presented.
The key here is to bring something fresh to the table, or to shine a new light on a topic by presenting it in a way that no one else has noticed or mentioned yet. There is little artistic value in just talking about sex, which is why everyone stopped caring about Howard Stern years ago. Some comics have made careers on doing strictly dirty material, however it is becoming more and more rare due to the fact that audiences are constantly evolving and becoming more and more appreciative of clever and smarter (high brow) material.
The clip I have attached below is from Donald Glover's episode of Comedy Central Presents, which shows exactly what I am talking about here. Enjoy.
