This football season, Amazon-owned Twitch gave users the ability to stream Thursday Night NFL Games on their own personalized channels. And as executives soon discovered, the biggest audience on the platform hasn’t come from the official stream, but from an individual user who adds his own commentary to the game. Twitch COO Sara Clemens sees this as evidence that its millennial audiences are more interested in insights from their peers than professional commentary.

And it’s why she argues live television will ultimately move in the direction of commentary that viewers choose themselves. Unlike the experience of watching TV shows and movies, which has been upended by on-demand services like Netflix, live television hasn’t evolved in 50 years, Ms. Clemens said. But that’s poised to change.