No one's actually made a gaming tablet with physical controls with any real support put behind it.
Nvidia made the Shield tablet, but the tablet one they released last year didn't have any buttons. They released a fold out screen one attached to a controller before that, but that form factor is more similar to the 3DS/DS. That's not what the OP is talking about either. Unless you're counting those Korean knock-off type devices, but really if you're doing that you're grasping at straws.
In either case neither of these were carried by most US retailers, had no marketing campaign, and no exclusive games. A Nintendo tablet carried by every retailer, with marketing, exclusive games, etc. is a completely different story.
Also the original Game Boy was hardly pocket friendly, yes the thing was small-ish but it actually had the thickness of a brick. I pretty much always used to put in my back pack, there's no way it would fit in my pant pockets. An iPad mini while technically larger is much easier to carry around because it's far thinner and lighter.
And 26 years they've done it this way ... so what? Nintendo's suffering it's worst yearly handheld sales in 18 years right now. Obviously what they're doing in the handheld business right now is not resonating the same way it did in the past.
Nintendo also only made single screen handhelds for 15 years ... guess they should've not created the DS then, because change is apparently bad, mmmky.
























