I need an answer from a Jehovah Witness! especially someone under 30! help?

I have a close Jehovah Witness friend and we hang out a lot. I'm not a JW but i grew up with him. i do some bible study with him just for the heck of it. We have a lot of mutual friends who are not JWs. I don't get why he doesn't want to hang out with his non JWs friends. Since I'm too embarrassed to ask him that question, i'm really hoping a JW can answer this question who are in the same position. We have this mutual friend who is a little crazy. He's calling him out because he's always making up excuses. I really feel bad for my JWs friend because our mutual friend are talking about him saying that he never goes out with us. Straight to the point! are all JWs like this? Do they make excuses all the time? Why don't JWs don't go out with non JWs? I also want to know, what are good excuses for him not to go? so i can help him make stuff up.