Well, first off, welcome aboard, Matt! Happy to have new folks stop in.
I guess you can say that making maps is the game for some of us. Others have games (mostly role playing games I suppose) where the maps serve as accessories, and others still use the maps for publications - along with their novels set in the world described by the map, for example. In short, there are plenty of reasons to make maps.
A cheap (free) way to get into role playing games could be to download the open beta version of the Pathfinder RPG from Paizo (http://paizo.com/pathfinderrpg) - I'll warn you that role playing is rather addictive (or can be, at least.)
To get you started, I'd suggest you try out a few tutorials, see what works for you. You'll need some software, and again, I'll suggest a free option: the Gimp (http://gimp.org/) is available for both Windows and Mac (and Linux of course), and there are quite a few tutorials for that one.
Thanks for stopping by, and once more, welcome!