Why haven't I joined the NRA? Simple:
$$$$$$$$$. I have none. I'm lucky if my wife and I can pay our bills each month. With 3 hungry mouths to feed and college loans, an NRA membership has to wait. I wanted one from my wife for our anniversary, but we don't have the money (we're getting each other cards). As for the price of a box of decent ammo... I don't have that, either, at the moment (heck, I don't even have my AR completed!).
Why do I want one:I've only been a gun owner since May of 2000, when I realized I'd have to move into a not-so-nice part of a big city and leave my wife and kids alone at night while I worked. That convinced me that a gun was important. Before then, guns just didn't register on my radar. I was much too interested in medieval weaponry. Once I got a gun I started researching gun ownership, self-defense, and the 2nd Amendment. By the time I realized the importance of RKBA organizations, I didn't/don't have the $$ to become a member.