I think Nintendo likes having a platform dominated by their own software and not having to compete with the mainstream 3rd party titles.
NES, GB, N64, Wii, DS all averaged about 40% of total software sales coming from Nintendo-published games and averaged about 40 Nintendo-published games to surpass 1 million units sold. On the other hand, SNES & GC are the two Nintendo devices with the largest amount of multiplatform titles and Nintendo-published titles only make up about 25% of total software sales with only 18-25 million selling Nintendo titles.
U could argue that this shows when Nintendo devices get the mainstream 3rd party titles that their own software sales take a hit and I don't think Nintendo wants that. The type of 3rd party support they want are games that will compliment their own software and games that are exclusive.
When the herd loses its way, the shepard must kill the bull that leads them astray.
