[poofyhairguy]

Same reason Apple TV can do it. The app authors have written in support for it on their Fire TV and Apple TV apps (it's not Automatic AIUI - but API controlled - and few Fire TV apps support - Netflix and BBC iPlayer didn't last time I checked) but haven't on Android TV - so I guess the issue is more with app authors (though could nVidia do something bespoke like AMLogic used to?)    

We can have autoframe rate on apps with refresh rate tool on Shield TV, then Why Nvidia can't integrate it on the system itself ?      

I guess to avoid the problem Roku have had with their Streaming Stick + and system-wide frame rate switching.  Roku have disabled it for Netflix (and only Netflix) because of the autoplaying of trailers in Netflix I believe.  As you switch between shows and the background trailers auto play, if they are different frame rates, you get a display re-sync and a couple of seconds of flash-bang resync on your display, which is very annoying as you scroll up and down slowly to read synopses.  If the refresh rate is API controlled, you can avoid this.   

Exactly the problem I have run into with Rokus and Netflix. It basically breaks the interface to a lay person. That plus a lack of Dolby Vision support is why I don't like using them as a streaming option.

I would love for that Nvidia stick to be my main streaming option if they get that working.