I'm no Apple insider, but my hunch is that 32GB is right in the sweet spot of what most people probably realistically expect to use. So, basically, they could easily give you the 32GB in the baseline model, but they know that if they do that, they'll be leaving a lot of money on the table because there isn't a stark difference for a large percentage of users between 32GB of storage and 64GB. 16GB on the other hand is a different matter.

The fact that so many people are complaining about this is probably a sign that, if that is indeed the reasoning behind the lack of 32GB model, it was a smart choice from a profit perspective.

So the better question is: how is Apple getting away with selling a 16GB option for $500? It's not really that much space, especially when you take the OS and the space necessary to download updates into account.