Well, this poll and the thread really proves my point that the whole "[insert game here] only has succeeded on Wii U because Wii U owners are starved and the game has no competition" argument is dumb for the most part. The overwhelming majority have a PS4, Xbone, or competent PC and possibly a 3DS or even Vita. Consoles aren't like countries, you don't have to go through a thirty step process to get dual citizenship :P
You're looking at different results than me. The majority only have a Wii U and 3DS, and a PC. We have no idea whether those PCs are competent or not for the most part. For all we know they're using those PCs for web browsing and word proessing, etc.
The trend based on the results in this thread so far:
Most Wii U gamers also have a 3DS.
Most Wii U gamers do not also have an X1 or PS4.
This really shouldn't be a surpise to anyone. For example, I bet you don't know of anyone that owns 2-3 PS Vitas, but it seems pretty common amongst Nintendo fans to own multiple versions of the 3DS. Of course, not even the majority of 3DS owners are that way, but I do know of one person that owns 5 3DSs and just pre-ordered the Super Famicom 3DS from Japan. In my experience Nintendo fans appear to be very very loyal to the breed.