You don't grow out of enjoying something. Sure, you'd never catch me dressing up at a convention, but that's because I'm not lame. But I get it.

[His inner nerd would love to dress up at conventions, but he's got an image to maintain. An image that apparently involves wearing expensive clothing and being 'ttly cool'.]

It's sharing appreciation with others, of belonging to something. These people aren't just here for us, they're here for each other. For some of them, this is the only time in their lives that they can just hang out and be themselves and actually get approval from it. They can dress as their favourite hero and have others actually giving them compliments for it rather than laughing in their faces.