Why do so many apps still lack AirPlay?

Apple announced airplay over 2 years ago and we all knew it was the future of watching tv. Some major players added the technology to their apps quickly. But still almost 2 years later most of the major players still lack this functionality. Just look at the brand new NBC app. No airplay. Why is this? Are television makers afraid of the technology? Does it hinder their ability to display ads?

im really just trying to see what your opinions are of this.