I think Nintendo's big worry has always been account sharing. It's not about buying one copy of Pokemon for the kids to share. It's about the college student buying one copy of Pokemon for the dorm
The reality is that this is another "feature" that "N" doesn't understand, or want to be a part of, so they dismiss it, or just don't allow it. Sharing apps and games across devices within a single home or among close friends has been a standard feature for awhile, and just like trophies/achievements, netflix, web browsing, cross buy, or any number of standard features, it doesn't matter if they understand or like the feature, the point is it's a "selling point" at retail, that can be the difference between a purchase or being passed by.
It's no different than having 2 kids each with their own gameboy, and letting both kids share a library of games. "N" just sees it as a way to have one buyer, or a single family buy multiple items across several pieces of hardware. The same reason they sale a $100-$200 N3DS, a device that requires charging, and yet does not include a way to charge it out of the box, so you have just spent hard earned money, but wait, now spend another $10 for a charger. That is just bad business. I don't know of a single handheld device that needs to be charged, that does not include a way to charge it within the box(smart phone, tablet, kindle, etc.). If a device has an internal battery, you give the buyer a charger, that's just nickel & dime BS.
Once again, when the average consumer sees the NS at retail, and then realizes the features it lacks, along side every other device within it's price range(below or above), the choice becomes easy. Once again, if they want to compete, which they have said many times, they don't(which I 100% believe), they need to offer comparable features, at a comparable cost. If your not willing to do that, why are they even in business? And it's rather easy to cap the usage of a single purchase to 2-3 users within a single family, so the whole college playing Pokemon doesn't fly, as that is an easy fix.