If you feel the market wants the Wii U, then why is everyone buying these other consoles over it?
Games. The Wii U has no games. Nintendo released the system before it had any major 1st party games aside from Super Mario U and Nintendoland, deciding to rely on third parties to round out the launch only to find that third parties are horribly fickle. They release crappy ports and cheap cash-ins to test the water to see if the Wii U will be an instant hit, and when the sales start to tank after the holidays, because there are no good games, it is pronounced DOA, and all but a few developers abandon it. So, until Nintendo can start to release their AAA franchises to gain some momentum, who's going to buy it?
As for the Wii and PS3, The end of the generation is one of the best times to get a console. You can buy a new console for dirt cheap, and then acquire a huge library of (new and used) good games for next to nothing. Plus you have the filter of time to know what to buy and what to avoid.