sounds like he's a young guy, this maybe typical, the kind of person i am i would sneak a kiss and that would be it. as if i m saying "if your afraid of your friends going to tease you then, here let it be over with".

it could be other reasons, some people are peer-pressured with somethings. they might've made jokes about him being whipped and he doesnt want to appear that way in front of his friends.

how old is he? he's probably still insecure around his friends and afraid they'll make fun of him...this typically has to do mostly with age

Some people aren't very comfortable with seeing other people's PDAs. He may not care if it's people he doesn't know, but around his friends, maybe he thinks it will make them uncomfortable.

I mean, haven't you ever been around a friend and her boyfriend who won't stop being touchy-feely? Doesn't that make you a little uncomfortable, especially if your boyfriend isn't there? I'm not saying you guys would start full-on making out, but even a little kissing and cuddling isn't always appropriate around other people.

You might also consider that not being overtly affectionate makes you more part of the group, rather than his tag-along girlfriend.

hey, i have been through that. the guy (if he is like me) probably isnt ashamed of you in anyway but he just doesnt want to seem soft in front of his friends. if he isnt a tough guy it might also just be that he hasnt had that many girlfriends so he is insecure.