Its because the rest of the world builds cars to spec, how they want them when they want them.

In Switzerland, one goes into a dealer, plays around with the demo (or waits 1 week until the dealer requests the demo that is close to what you want and has it transported to the dealer), then puts in an order, and waits 4-6 (6-8 months on a high demand E70) for their ordered car to come in)...

Dealer's do not have the liberty of placing hundreds of orders and creating inventory, like here in the U.S.

The rest of the world doesn't have this, "I walk into the dealership this afternoon, and drive away with my new BMW tonight" mentality...

So then your saying, well if I special order, why can't BMW just put the orders through then? It could, but it won't. BMW, nor the dealership has no guarantee that you will take your order. Under law, it has nothing that prevents you from not taking your ordered car. Therefore, unless its an M car, or later in the production cycle, and your willing to pay some extra $$, BMW NA will most likely deny your claim for a custom vehicle.

Another thing to consider is perhaps how the used market in the united states works. By keeping options relatively simple, BMW is able to simplify the searching and pricing of used cars (less variables), as-well as keep its resale price high (by eliminating unpopular options/color combinations).