Wii online was terrible, but that was 2006 technology. From the games I played online with the 3DS, the games run really smooth with no lag or choppiness at all.
I can't say about the Wii U, but I'm sure it's not as bad as you're trying to make it out to be.
Of course they care, that is why they're the most successful every generation since their inception.
This leaves Nintendo the only platform to not charge their players with an online fee. Plus, I believe Miyamoto said something along these lines just the other day that made a great point.
"PS4 and Xbox One would easily cost $100 more if they included a gamepad".
Even more true for PS4. At least the Xbox One has a built in Kinect.