If the guy you're dating doesn't introduce you to a single one of his friends and keeps you completely hidden from them, it's a red flag that he thinks he could do better, or potentially involve those six lethal words (hint! ends with: "not that into you").Oh, you mean you want to be secret friends? No chance, Shane West.
He likely wants to continue to be seen by his friends as the ultimate bachelor, ready to game on anything he considers a "7 or above," and has already introduced too many of your kind to his friends he doesn't want to have to explain what happened when you stop appearing. If your interactions with his friends have been merely brief encounter when you two rendez-vous at 1am, feel free to guiltlessly accept an invitation for drinks or Mr. September's offer to grab a bite now that CFA is over.