So it's widely known as a fact that many Nintendo games have ridiculous legs. But here's the question that no one really bother to ask...why is this so?

[NightDragon83]

Because during the Wii generation Nintendo basically figured that as long as the casuals keep buying the same games over and over again (Wii Play, Wii Fit, Mario Kart Wii, Mario Party 8, etc etc), they don't need to release anything else and can sit back and watch the money roll in.

Seriously, this has been their strategy since 2008... release one or two games a year that do well with the casual crowd, and ride out their sales for as long as they can.