lol, what a great thread. I think I echo what a lot have said. I enjoy the "working on them" part of it. Quite frankly I've read articles about retirees driving their wives crazy hanging around all the time and I wanted a hobby that got me out of her hair. I looked at restoring classic cars but the cost is too high and I knew she would not go for having a bunch of junkers around.
Pinball fit the bill quite nicely and I really enjoy the repair process, not only the visual stuff (paint, repairing plastics, etc.) but the internals. I didn't know much about electronics- still had my soldering iron I got from Radio Shack in 1975 in a box - but I am learning.
Plus the actual playing is a lot of fun and my goal is to have a few games available and looking good for when friends and my sons come over.
I've only been into this for a year so its all still new, I think it is the wide variety and fun factor that keeps people in the hobby. Tired of this pin, swap it for a different one. Tired of working on electronics, make your own translite or slide on decals, or learn to airbrush art or start modding, etc. there is so much to do.