Because it's being sold. For the (I suppose moronic) people not ready to wait it out, it's a legitimate reason not to buy the game now.
Au contraire, there's no reason not to buy the game now. You can fly around and get a feel for the game, plus Vanduul swarm is really fun (albeit for limited amounts of time), especially co-op. What you
shouldn't do is try to be the bestest PvPer ever in an alpha -- or if that's what you want to do, at least not whine that at the moment the best dogfighters cost more money than the multi-purpose starter ships.