I'm probably one of the audience members that doesn't seem to "get into" the music, no matter how much I like it. I don't make silly faces and dance in public, because thats not something I often do in my spare time. A lot of times "cutting loose" and dancing are two opposite things, for me.
In punk and metal there has always been the "stone" audience members that will dig you but they're not moving. Still, I don't get the selfie garbage - self-centered narcissists.
If I have to bounce around and scream and flail my arms and bash into the sweaty stinky drunk guy next to me to be a good audience member, then I'm too tired from working I'm staying home. Playing the "crowd member" is just a lot of work. If I can stand back where the speakers aren't jacking holes in my eardrums, relax and chill and enjoy the band, great I'll come. I'll even clap louder than the rest of the people in between songs.
I don't know how much alcohol or what exactly I'd have to consume to be flailing around like the people I see at some shows, but I have crap to do tomorrow, and Fonzie didn't raise no fool. Mosh pits irritate the poopie out of me - I'm trying to watch the show and a guys trying to teabag my neck, inevitably someone doesn't take the warning or starts stomping on a girl and I have to "mosh" them back. I didn't come out for fight club I came out for music.