Hmmm, Your response strikes me as niave.

What I said is that Nintendo won't drop the 3DS anytime soon (they've got tbc 2017 titles so I'm likely right) and that its got another 2 years worth of software support, emphasising 3rd party support because thats where most of it will come from at its end life. If you follow gametsu and the like, you know 3DS titles are still being announced every week, we already have a solid line up in 2017 for legacy platform which could comfortably sell off its back catelogue, so thats 1 of 2 years sorted. Nintendo are the same company that released Pokemon Black and White 2 exclusively on the DS well over a year after the 3DS was released. Even with Switch as their priority, I expect them to drop a few bones for the 3DS audience here and there (getting their monies from the still huge userbase) and for them to push budget value 3DS bundles well into next year. The 3DS will naturally fizzle out, which is an entirely different concept from Nintendo all at once pretending it doesn't  exist.

There are so many potentials answers to your question of why they wouldn't have a dedicated handheld out the gate, but the question itself is no more interesting than why did Nintendo not have the 2DS available at launch? Away from all of the marketing and buzz words, Nintendo want a streamlined development and revenue pipeline. The "NX" needed to a beast of a portable to carry support from Wii U titles and share them amongst Nintendo's future home console. If they followed the unified software route it was always going to have a much shorter battery life to what Nintendo fans are used to and it would struggle containing its specs inside the typically small shell Nintendo portables have launched with. As the handheld market is in obvious decline, it makes sense for Nintendo to expand their horizons with a tablet hybrid and it suites their unified platform concept perfectly. Like all of their innovations/gimmicks they like to put it front and center instead of muddying the waters with a half hearted, optional approach. Arguably if it wasn't for the Wii U's failures we wouldn't be seeing a new portable as early as spring 2017. 

Similar to 3D, hybrid functionality of the platform has no barring on game functionality. As such if there is an audience and money to be gained by later (when its physically possible) creating a stand alone handheld device from, there is no reason why they wouldn't do it. Once they've hammered home for 2 years (look how cool our hybrid is!) they're going then turn their mind to people who don't want to pay for the portable function or those who want a cheaper, more handheld friendly device. They removed 3D from the 3DS and gave us the 2DS. Hell they even removed wi-fi from the Wii just for a few late life sales. They have never been afraid of having distinguished SKU's. Furthermore Nintendo are not daft, they obviously know a huge, power hungry, $250-300 tablet is not a 1:1 replacement for a $150, pocket friendly device. When they gave the PR statement of "its not a replacement for the 3DS or Wii U" they were being genuine in more ways than one. The Don Matrick statement is funny but it holds true for now. Not all of the 3DS audience is going to be comfortable with the Switch in its current form and thats ok.