Because Wii U is not competing with with PS4 and XBOne this year. PS4 and XBOne will launch this fall at prices of $400 and $500 respectively. They will be in somewhat limited or perhaps very limited supplies. Like the Wii U last Christmas, virtually every PS4 and XB1 that arrives in stores will be snapped up before the season ends. Pretty much everyone that buys one this year will be a fan, someone who is anticipating the system for months or years, and the bulk of customers probably pre-ordered it. As such, none of these potential buyers would walk into a store and say "hey, there's a WiiU Deluxe for $299...that's cheaper, I'll buy that instead."
All of the potential Wii U customers are buyers that want a Wii U for what it offers. Some may be put off by the price, but these people won't be picking up a PS4 or XB1 instead. They may hold off on a purchase, or buy a PS360 - but those potential customers are dwindling with market saturation and fading appeal of old product. Some may get a 3DS. Since there will be so few PS4's and XB1's in the world, they won't be competing in the mainstream market until 2014. Wii U has this sector to itself (among new home systems) for the time being.
Reducing the price of Wii U will most likely just cut into Nintendo revenue. A loss of $50 per system is a lot of money. If conservatively 5 million Wii U's are sold through the end of the year, that's $250 million in lost revenue. A price cut would have to generate many, many more sales to make up the difference, and I don't think this is likely.
So I think we'll see a price cut for Wii U in 2014, once PS4's and XB1's become readily available on store shelves. When non-partisan customers are wandering Best Buy thinking about options, the $299 Deluxe could be a selling point. Right now it doesn't matter, especially with XB1 sitting at $500. A $299(or less) Deluxe Wii U could hit along side MarioKart 8 in spring 2014 as system makers really begin to push for the every day buyer.
The only way we see a price drop for Wii U this year is if sales really, really stagnate in the second half despite new software launches. If it really seems the public is rejecting Wii U, a desperation price drop could be done to get the product out there.
