At Valley of the Blue Snails, Canecorpus discusses setting design as a hobby. It's something I can identify with. I enjoy role playing and I enjoy setting design, and sometimes I enjoy them entirely separately from one another. In fact I might go so far as to say that I like setting design even more than I like gaming. It's a great way to express creativity, especially if like me you are a terrible artist (regular readers will attest to this) and cursed with a flea-like attention span (precluding novel-writing); moreover I would call it a pure hobby in that there's no way that a setting-designer can possibly be in it for the money. You don't sell stuff like Yoon-suin on its own, at least not in numbers. It's a labour of love, and that's that.
Today I had a godawful hangover and crippling aches and pains from playing football last night, so I spent most of the day making maps. For inspiration I visited the Cartographer's Guild, and from there came across the amazing Sorol, a one-man effort to collect the "accumulated knowledge about the planet [Sorol], its inhabitants, and its history". The creator is not a role player and as far as I can discern just makes it all up for fun. (He makes, quite simply, the best maps of nonexistent places that I've seen.) It's good to know one is not alone, and even better to know that there are people out there with such skill, energy and motivation. It serves as a kick up the backside.
Of course, world creation is a venerable practice. Tolkien originally made up Middle Earth as a hobby and a way of providing a history for his created languages. The tradition continues to this day: one of the most interesting modern examples of world creation, Ill Bethisad, has similar origins. First created as an alternative history to explain the existence of Brithenig (a made-up language based on the premise that Latin in the British Isles did not die out), it is now a highly detailed world all of its own, with several constructed languages and a complicated political structure. Believe you me, if I had the linguistic knowledge I would also be making up languages myself - probably right this moment.
Beats watching TV anyway, right?