I'm looking through the Play Store for more games that I can install on my Nvidia Shield, since friends and family and I all like to play games on the thing. I've come across so many apps that have controller support and are fully navigable with a controller, and some that even have controller button prompts and instructions in their app. With all that, you technically just have to mark your app as Android TV compatible, throw on some nice artwork and bam — now you support Android TV.
Yet, there are so many apps that don't do this. Notably missing is Punch Club, which was launched just a few weeks ago. Shovel Knight and Surgeon Simulator are two other notable ones. LIMBO is a big one, although they claim their reason for not giving LIMBO any sort of love is because they're focusing all of their attention on their new title INSIDE for XB1.
Then you have your apps that work perfectly fine with Android TV, are able to be installed to Android TV through the web version of the Play Store, they even show up on Leanback launcher, yet they don't show up in the Play Store on Android TV. Alto's Adventure does exactly this (beautiful game though!). As a bonus its also fully playable with the regular remotes for Android TV.
I just feel there are so many titles that could be on Android TV and aren't. It's such a good platform and the only thing it's missing is the apps to really support it. It's slowly picking up, but it could be so much better.
The best you can do is contact the devs. We're in a chicken/egg situation right now, much as regular android was years ago. The benefit this time around is that the ecosystem already exists and the devs already exist. We just have to show them that there are customers that want Android TV support.