Can the poll be made multiple choice? I found it limiting and not really accurate for me to pick just one answer. I couldn't decide on one, but make the following post to explain.
My primary reason is for the fun of exploration adventure. Since as young as I can remember I have always been an adventure explorer. As a child my idea of fun was not playing at the park, not doing sports, not playing board games, not watching cartoons or other tv shows, not even playing with toys...
I liked to go out on my bike and explore places I hadn't been to. A new neighbourhood, the local creek or lakefront, abandoned buildings, contstruction sites, anything not normally easy to access or open to the general public, places most people didn't go or want to go to. The bike was a means to get to the adventure as well as a test in itself to see how far I could get before I had to walk. I guess from an early age I was interested in mobile exploration/adventure. I've been that way ever since.
As a teen in Edmonton I, with likeminded friends, wandered in the River Valley, explored various locations around the city, infiltrated abandoned buildings and otherwise went into places we shouldn't be. By this time however we were using both bikes and cars as some of us were coming of age.
As a young adult with trucks/cars of my own, the adventures became further away. Long distance exploration took the place of city-bound travels. My first wife and I used to load up our car every weekend and spend a day driving around Alberta looking for ghost towns or abandoned farmhouses or other long forgotten, unmarked historical locations/places. The research was part of the fun for me, the actual "find" was a reward for long hours of painstaking mapping, cross referancing, and hours of digging for information to pin-point these typically remote and overgrown sites.
It remains the same all these many years later. Jeepin', exploring, and goecaching all together like a well oiled machine. The fun and the adventure is still there. But the long hours of research have been replaced by a few minutes; and the paper maps have been replaced by a little hand-held map machine using high-tech US Government equipment. This is not to say that I don't still do full scale adventures that require hours and days of research, mapping with real maps, and myriad other activities, I do. But, Geocaching has become a great little way to provide and manage bunches of "mini-adventures" in between my larger more detailed ones.
Such is the reason for Prairie Jeepin