I don't know about most consumers, but I have more than one console, as do most of my friends. And I don't know that you can say the Wii U is outselling the Xbox One at the moment, since Microsoft hasn't released sales numbers in a long time (because they can't stand the fact that the PS4 is beating them).

As for "current gen" consoles, the Wii U doesn't compare favorably to the Xbox One and PS4 based solely on specs (it's not even close). Nor does it compete well on features, as it can't play movies discs (DVDs and Blu-rays), which is something many families still want, even in the streaming age. Of course Nintendo has proven time and time again that great gaming experiences can be delivered with lower-end specs focused mostly on gaming. The 3DS has been killing the Vita since day one, and the Vita has far better specs and arguably more features.

But the Wii U has carved out a niche for itself. But that's it--a niche. If you want to play an online FPS, which is something many, many console buyers want to do, you buy a PS4 or an Xbox One. If you want to play sports games, which again, are a big draw for console gamers, you buy a PS4 or an Xbox One. Nintendo is focused on bringing unique IP to the Wii U, and they are doing a very good job of it. They don't need to rely on third party IP nearly as much as Sony and Microsoft. It's to the point where many people are buying a Wii U purely for one game or franchise, like Super Smash Bros, Mario Kart, Zelda, etc. This is why the Wii U is likely going to be in third place for this entire console generation, whereas the Wii was the undisputed champ of the previous one.

Nintendo made a calculated bet with the Wii U, just like they did with the Wii, and this time they were wrong. They released a year early with low-end specs, and expected their gimmick controller (the gamepad) and promised game library would carry the day. For whatever reason, it did not. Personally I blame terrible launch marketing and very confusing product differentiation.