It's actually getting a bit boring now.
I'm too good for this.
Crack a smile dude ! At least look like you're having a good time ?
But it's his thing. If he actually started smiling or even looking halfway enthusiastic now, people would never stop talking about it. He's kinduv painted himself into a corner with it. Maybe if he just did it once in a while, worked into it slowly.
I never interpreted his attitude as being too cool for it, it's just that he doesn't really have the goofy/silly side that the others do. He's there, they're his bandmates, but he just can't bring himself to do the silly faces and stuff. I'm kinda the same way. Occassionally I'll smile in a picture, but that's about it. Maybe it's an Asian thing.