RE: The addiction?
I got bored with RC cars, probably because I never raced or went to tracks. But RC flying is a lot more interesting and challenging to me, and has held my interest for about 5 years so far. I don't care for the building part of the hobby, I just like to fly. I'm finally as good a pilot as I initially hoped to be, but I can still work on some more advanced flying, and that keeps it interesting.
I can go to the field and do my usual sport flying and relax and have fun, or I can work on some more advanced stuff that will keep me on edge, whichever I feel like.
With RC cars, theres only so much I can do before I get bored tooling around my driveway.