You know how sometimes, you want to read a really, really specific story... problem is, it hasn't been written? And if you ever say something along those lines, everyone tells you to go write it, then! But the thing is, you don't WANT to write it, you want to READ it, and everyone knows those are totally different things. Well, for me, roleplay is a way to scratch that itch. You get to craft that perfect story, and you don't even have to write it, at least, not entirely by yourself. You get that control over the plot, to a degree, but having other writers involved keeps that uncertainty all readers crave.
It's great.