In terms of hardware, almost all games are optimized to the fullest for the dual screen, flip style, stylus-based arrangement of the Nintendo DS. It is for this reason that I very much prefer playing games on the DS as opposed to on an emulator. The DS games simply lose their feel when played outside the console, while some games like Brain Age, actually become semi-unplayable.
The crew of various companies put a lot of work and effort into polishing and refining their product to the max before delivering it to us. And to say that we aren't going to give them a penny in compensation, and just download the game off the internet to play on an emulator is just plain disgraceful, I feel.