It is simply because you are not even allowing yourself to see the benefits of having an indepth game on a mobile platform. Baldurs Gate is the perfect example of a game that has complex game mechanics, yet low system requirements, so it should be possible to port to a mobile device like the iPad. I feel that a turn based game would work better (like say Fallout, Civilization, or HOMM) since it will be difficult to use the touchpad in real time the way you would with a mouse and keyboard, but it is a slow paced game and the mechanics are turnbased (although constantly running).
The point is simply that there aren't many complex options on mobile devices that aren't Gameboy type devices (I can't think of what a mobile gaming device would be called, perhaps just "mobile gaming device"). I for one would like one. I have times when I would like to do something more than a simple puzzle while I am stuck somewhere by myself (like on an airplane, or when I am laying down with my daughter trying to get her to fall asleep.) Simple things like Angry Birds, or Cogs, or Drag Racing just don't keep your attention for very long, and get boring quickly. A complex game you can get into like Baldurs Gate on the other hand could keep you interested the whole time you are in the air.
That doesn't mean that the iPad would replace the PC as your primary gaming device, but it just means that there is no technical reason you can't play indepth games on the iPad. I can think of plenty of reasons to play those games on the iPad as well. Saying that people likely already have the game on their PC so they aren't likely to buy it on the iPad is kind of missing the point. The reason for having it on the iPad, isn't to be able to play the game when you are at home with access to your PC, but instead to be able to play it when you don't have access to your PC.
