APO shipping and Sales Taxes

I am stationed overseas, as are many service men and women. Unfortunately, we are unable to purchase iPhones from the PX/BX over in other countries. We have to purchase from Apple, and then ship to a forwarding company. On top of this, we are charged sales tax based upon the forwarding company address.

Why won't Apple just use the Post Office and ship to APO? We will pay the postage fees! Why won't Apple at least remove sales tax since the item is being transferred through an intermediary?