Why does my Nimbus controller become inactive when using Airplay to play games on my iPad but have them projected on Apple TV 4?

I waited for the SteelSeries Nimbus controller to come out and purchased it so I can use it on the Apple TV 4. I have games on my iPad that are not out for the Apple TV 4. I wanted to use the Airplay to have my iPad projected on my TV through the Apple TV 4. When I do that I can't use my Nimbus controller to play games. Why does my Nimbus controller become inactive when using Airplay to play games on my iPad but have them projected on Apple TV 4?