I really think that would have been cool as an actual game...it sure would have helped to sell more DS's, I'm positive.
Nintendo doesn't need help with selling DS's, they already sold more then 50 million... So you would be !@#$% dumb as developer if you are not going to make games for the DS.
Yeah, highest installbase is the best reason for development.
You'd have to be nuts to develop for systems other than PS2, PC and Mobile phones.