In May, we learned that Electronic Arts has essentially stopped publishing on Wii U. At that time, company spokesperson Jeff Brown didn't specifically cite a reason. Many assumed the move was related to sales, and late last week that suspicion was confirmed for one title.
Speaking to The Sixth Axis, Need for Speed: Rivals creative director Craig Sullivan stated that last year's Need for Speed: Most Wanted "didn't really sell that many, in terms of the Wii U market." Most Wanted also appeared on the PlayStation Vita, another platform that Rivals won't be appearing on.
EA developers have also stated that Frostbite 3, the engine powering the publisher's non-sports, next-gen games, isn't running on Wii U. While this statement was made months ago, given that no games are in development, it would seem that no further progress has been made to rectify that situation.
[Source: The Sixth Axis]
The fact that Need for Speed: Rivals is skipping Wii U isn't surprising. The important thing here is that Sullivan put a fine point on the reasoning. EA does not currently deem Wii U development a worthwhile investment.
It's important to understand that if development cost is greater than likely sales, then publicly-held companies have a fiduciary obligation to not create that product. Nintendo absolutely must start incentivizing third-party publishing if it hope the Wii U to flourish.