They do that to protect the dealership/installer network and to protect the profit margin on the more expensive projectors. The HC9000D was an even more extreme example of this thinking. Mits and others have to decide if they want to sell more PJs or keep dealers happy. The conventional wisdom would be that selling more product at a reduced margin would be better than selling a few at a higher margin. I think in this case, conventional wisdom is right.
I avoided the HC9000D specifically because I did not want to pay someone else to install the unit when I could do an equal (or in many cases better) job myself. I also didn't have any interest in supporting the dealer's margins, at least for the dealers I tried to deal with. When I contacted purported Mits dealers about the PJ, they didn't stock it, but they could order it at full price if I agreed to let them install it. Of course, I'd get a "free" evaluation of my room and system, too, with suggestions on how they could upsell me to stuff I don't want or need. For them, full price was $9,995, but with an install the discounted price could be $6,995 for the PJ. Installation including a ceiling mount would be many hundreds more. What a deal!! Especially for a PJ that's currently going for $2,999 from AVS.
Mits is ducking out of the high-end market because the strategy failed, but now I see they want to ruin the mid level market by bringing this moronic limitation to the HC8000D. Good job, that.