Because when I look at their system the only promise I get is that I will be able to play Nintendo games.... That's it... There's nothing around Nintendo that tells me "this console will bring you joy and hapiness for X years" just "Nintendo may or may not support this console, but buy it, cause it has some really cool shit on it".
I love Nintendo games when we play with friends (the poor soul dared to buy a Wii AND a Wii U) but that's it.