Why can't I play the tour levels without network?! It makes no sense, and seriously undermines the value of the app as something to do on the train.
Nintendo amazes me: as an organization they make incredible games yet are terrible at everything else.
Don't forget, they are very new to mobile. Things that may be obvious to mobile devs are overlooked by a large company used to a captive console audience. Nintendo doesn't move quickly but they are very adaptable in the long run.
It looks like it's either console devs doing this, or Nintendo wrote some strict console-like requirements. Like login before you see anything and "you have to interact after the loading screen" silliness.
I refuse to buy it purely for this fact. Not because I want to pirate it, but because I do most of my mobile gaming while on a plane. And I'm not paying for in-flight WiFi just for Mario.
The Duolingo example is an excellent illustration of good practice.