non-nintendo games don't sell well on nintendo systems unless there's a significant drought in nintendo-made games, and even then the sales aren't stellar.
unless the switch sells gangbusters within it's first 6 months (6m+) most third parties aren't going to do anything, and the ones that already said they would, will either release one and cut and run, or cancel and move on (a-la wiiu), switches biggest problem for third party support right now is that the only gimmick it has in it's favor (portability) adds nothing new, and until nintendo nix the 3ds line theres little reason for 3ds gamers to "switch".
Also say you're making a game, you originally planned pc, xbox one and ps4, each userbase potentially millions of sales, then you turn to switch within it's first year and your potential sales drop significantly, to a point where the cost of releasing on the platform cuts so hard into the profit margin that most studios will play the waiting game.
it's a vicious cycle, they play the waiting game and the console goes without third party support, thus userbase expansion increases much slower, so when they revisit the idea and the userbase is still low, they pass again, cycle repeats.
It's both the fault of third parties for not investing/taking a risk in the platform, and the fault of Nintendo fans who put nintendo-made titles on a pedestal, and buy almost exclusively, nintendo-made titles. There's a reason why theres a stereotype behind this buying behaviour only for nintendo gamers, and not for microsoft, sony, or even sega. - That inherant preference to buy nintendo-made over third party means the few studios that bite the bullet and release something, get mediocre returns.
Need for speed wiiu was a perfect example of this, the best console version of the game, performance and visuals wise, a game criterion slaved over religiously, and beyond being used in a few bragging wars, was mostly ignored.