Here's my reasons why.
1. Power. When Nintendo was planning NX, the main competition was Xbox One and PS4. So they make NX into a modest system, thinking that the bar would be low. Instead, Sony announces Neo (now the PS4 Pro) and MS announces Project Scorpio. NX is dwarfed by both of them. Now 'kinda' in the range of Xbox One is being below the lowest bar. We also see why Reggie had that sad look on his face at E3.
2. Caught off guard by Sony and MS. Never before have iterations existed on this level. Pro is over double the power of the base PS4 and Scorpio looms over everything else. Nintendo and most of the gaming public didn't see this coming. How could they? It never happened before. NX would have been perfectly fine if MS and Sony followed the script.
3. Price. Nvidia is expensive. Even if they cut Nintendo a deal, Nvidia is always an expensive proposition. More than likely we're going to be seeing this machine come in around $299. $70 more expensive than the base Xbox One. As expensive as the Xbox One S with UHD bluray playback, or the PS4 Slim, which is still many times more powerful than NX, and comes with an established library of games.
The NX launch is supposed to be 5 months from now. I'm thinking that Nintendo is desperately trying to find a way to turn this into some positive, but I think they are afraid to reveal NX because when they show it, it will be widely known that what they are revealing is Wii U 2.0. Another gimmicky, underpowered mess that will be ignored by 3rd parties for the next 5 or 6 years.
So what do you think? Is Nintendo afraid to reveal NX? Do you think that there will be a massive blowout reveal this month? Maybe next month? Or maybe a delay until holiday 2017 to try and make things better?