What you are proposing is more like selling someone a ring, shipping the diamond first, and then the base later.
But then you artificially skew demand to what is available in the store, while if you had let people order what they wanted to, you might have gotten a vastly different and more optimal sales mix. Apple will have a much better idea with the next release what people want.
If they had done what a bunch of "crazies" on a forum suggested, something else would have gotten screwed up, and the "crazies" would have suggested that Apple should have simply sold complete packages.