Role-playing, S.C.A, and reenactors

Don't expect this one anytime soon it's going to end up being kind of complicated but I want to look into role players, what's come to be called LARP'ing, the Society for creative anachronism and reenactors in general. This subject is so vast in its array of options, from people who dress up and play dungeons and dragons, or live action role play as vampires or other creatures, cos-play- dressing up as your favorite anime or manga characters, SCA, who recreate medieval times to the point of learning ancient skills, ren fair time tourists, comic and sci-fi cons, reenactors reliving civil war or roman battles, even those who dress up in furry costumes or as plush toys. Why? It must be more than just a hobby, or an interest in a time period, more than simply becoming your favorite character, so why? This has always been of interest to me, having been made fun if wearing a gi, why is this exceptable? Or us it? Believe me there will be an update and I'd love comments on this, if you or someone you know does these things.