Originally Posted by ocellaris
Well if you are talking about actual custom stuff, it is because just offering that type of stuff is expensive. There is overhead associated with every available option and part. Once sold, Subuaru still need to support it and warranty it, so if someone tears their custom pink leather or cracks a whale bone shift knob, Subaru can't just order another one like a normal item. This would lead to high replacement part cost and longer waits for customers. Eventually options will add the the bottom line of every car, not just the cars that have them.
A better question might be "Why can't I get a white Subaru with a black interior". That really just comes down to manufacturing, and when costs need to go down, so does flexibility
Not really custom. I have an accessory BOOK from Japan when I was there on 08. I ask to bring some, just some of what was in that book. They were/are all OEM things. I did talk to one of the guys responsible for our accessories at the Impreza training and some of it was explained to me. Again, it comes down to cost for the most part.