They all three have their way of doing business. Sony and Microsoft are big corporations so they can take more chance on taking a loss for marketshare which leads to profit with XBL/PSN and software. Though this is more directed at MSFT than Sony since they rely on Playstation more than MSFT does with Xbox.
Nintendo is a game company though and theyre not owned by a big corporation so its more important for their hardware to be profitable than PS and XB.
The Gamecube can be used as an example. I mean yeah it wasnt the best selling console of all time. But it sold moderately well and it profited.
The WiiU is likely to be even worst off than Gamecube when it comes to sales but nintendo is good at pulling out a profit. I think nintendo just needs to go back to the drawing boards for their next console and focus on making as much money as they can with the WiiU.
I still 100% believe that a lot of Nintendo's problems is variety and perception. And i believe they could change that if they tried.