To understand the importance of supporting an existing machine, you have to look at examples in the past that did it succesfully. Those we have are the PS2 and the Game Boy, these existed side by side in parallel with a new generation, and sold well for a long time. The success of these consoles solidified the respective company's presence in the market. The Wii, at the volume of sales that it made, was such a potential for that form of execution.
That's not true of the PS2 at all. The PS3 had a disastrous launch. The PS2 being successful did absolutely nothing for the follow up console.
NNID: theRepublic -- Steam ID: theRepublic
3DS - Currently Gaming Like It's 2011 - The Legend of Zelda: Ocarina of Time 3D
PC - Currently Gaming Like It's 2012 - Borderlands 2
Mobile - The Simpson's Tapped Out and Yugioh Duel Links