Its because they design their consoles with only their developers in mind, they don't go out and talk to third parties like Sony did.  

well nintendo has a lot of good devs, sony on the other hand ust have to talk to Naughty dog...

Offcourse it remained the same on Nintendo that is only logical. Playstation took over the 3rd parties they flurished on there. franchises that did not make the top 20 on Nintendo suddenly started making it in the top 20 on Playstation. Sony expanded gaming for 3rd parties on consoles.

Third paties suck anyway. They don't really try to do something new. They bring a new concept then and when but the control scheme is always the boring same thing: i.e. to run around with the left analogue stick, to look around with the right analogue stick, 1 buttion for a standard attack (weapon), another button for a strong attack (weapon), another button to change the weapon, shoulder button to focus... . It's always the same boring shit! (I know most of the first parties also use the standard control scheme but at least Nintendo tries to bring then and when something new).

I know right! Mario Party 10 all the way right!? *high five*

Not exactly sure why perfectly functional control schemes would need to be changed. Seems to be endorsing change for the sake of change. There's a reason Nintendo still use the exact same D-pad they always did. Because it works any no changes/tweaks ever improved on it.

It's a bit like complaining cars still have wheels and nobody has tried to do anything new.

Do you think that, if Nintendo decides to listen more to 3rd parties, their contribution to Nintendo consoles would grow, even if said console doesn't go as well as planned? Nintendo listening to their studios first is good, because their main source of income and their first harware seller are 1st parties by far.

Ofc their contribution would grow.  If the Wii U was x86 and easy to port to like the X1 is there would be a lot more third party games on the Wii U and ofc first party is thier main income they have next to no third parties...

Well, there is Mario.

And you don't believe that directly competing competing with Nintendo for a Nintendo gamer's limited money is part of that equation?  

Monster Hunter Tri is Capcom, not Nintendo... at least in Japan and USA. But one inaccuracy in the chart doesn't refute its point.