You do realize it takes time for them to redo the maps and make them compatible with the engine used in mw3. They can not just simply slap a few lines of code in and the map would work. They have to change the map file fairly extensively. That means time of the developers, that means money to pay them for doing so. That means the maps would not be free if they did more than just one like they did.
IW is out to make money, not give things away for free with out some sort of return to them. Plus if they made all MW2 maps playable in MW3 everyone would just sell MW2 or trade it in.
Plus people buy new games to play on new maps, not play on old maps from old games. Terminal was the worst choice they could have made and is proven by all the boosters that spawn kill on dom when that map comes up.
