Gee Gus, that's funny - I think the same thing about flying from a "real" runway! Call me crazy - after my first cruise and first 160 traps, I found 2 miles of asphalt to be rather anticlimatic... :)
OK, in the spirit of the thread, my reasons can be lumped under the "for enjoyment" department.
-It's relaxing. Just me, the kit, and the tunes. It can go as fast or as slow as I want - there's no deadlines.
-Creative outlet. I get to see it go from a pile of plastic to a 3 dimensional replica of something from real life - and it's MY abilities that determine the quality of that replica! Along with that, its fun to see my completed projects on the shelf and to share pictures of them with supportive friends and other modellers. The way the displayed projects and pictures start conversations is pretty rewarding, and it's a private thrill to see the progression of my skills.
- The subject itself. I mainly build jets - some of them ones I've been in, other's that I've been in some sort of proximity to (ie, I never flew in an F-18, but I've been in the pattern and on the flight deck with 'em). I guess it goes in with the creative outlet thing, but it's cool to bring to life a mini version of the same machines I've worked in or alongside (well, OK "work" is a bit of a stretch). I've also started building WWII and early postwar birds, and when i do those I really enjoy learning about them, and watching planes I've only seen in books or on the History Channel come to life in "living color" is really fun - at the same time, I can't help but feel a bond, a sort of "institutional lineage", with aviators of yore. Like when I build a Wildcat or Hellcat (since I too fly a Grumman product from a flight deck), it's a really neat feeling that's sort of hard to describe. Or when i do an RAF warbird - Churchills quote about "The Few" sort of echoes when I do one of those.
Oh, and there IS a sense of accomplishment when i finish one. That way I don't feel quite so lazy for not doing dishes! :)