The Wii is based on selling to casual players, who want a few "killer apps" for it. WiiSports and WiiFit are these killer apps. When you plan on selling fewer titles, you need to make a profit on the system. What I believe the Wii had did was cause publishers to give consideration to who is buying a system, in deciding what system to develop for. Just because a system has a top install base doesn't mean you develop a game for it.