The problem with this whole premise is that iOS i.e. the iPhone/iPad are assumed to be great platforms for gaming. Maybe this will change with the new gamepad options in iOS 7 but iOS devices so far have not been really good for gaming. Personally, I found several interesting games on iOS but all of the ones I enjoyed playing were strictly in the 'Casual and fun' category. There's something about the pure touchscreen interface that doesn't work for me. (maybe I'm old fashioned and the new generation of gamers are okay with just touchscreens)

This isn't to say that iDevices aren't viable gaming platforms - the hardware does have the punch. Could Nintendo make more money by releasing games on iOS ? Yes. Should they ? Well, I don't know if Mario for iOS will get the same kind of reviews it gets on their platforms. Do they want to take that kind of risk with their flagship icon/mascot ?

I know that Square Enix did pretty badly with the Final Fantasy re-releases on iOS. I couldn't take the controls.

Also, Nintendo makes money on hardware. Why forget that ?

I find the following questions interesting:

Why don't other major game publishers, who are ONLY in the business of making software, make kick ass games for iOS ? Why are we begging/criticizing Nintendo for not making games on a platform that most AAA publishers are rejecting anyway ?