The idea is simple. More views = More market share = More ad revenue, right?

People tend to watch the same streamers and it becomes a routine. In order to maximize the amount of time a viewer spends on Twitch, it would make sense to reward viewers to tune into new streams so they are able to find more streams they may potentially like, which in turn increase ad views on the platform in general. By giving people an incentive to diversify their viewing habits, you are encouraging viewers to find more streams they like. The time a viewer spends on Twitch will go up without them even noticing! It would also make Twitch more interesting for the viewer and help the viewer be immersed in the Twitch community. For example, think of it as a buffet. If you know there are a lot of offerings you enjoy, then you are more likely to go back often and recommend it to your friends. Anything stagnant becomes uninteresting and in today's society, where there are so many options to spend your free time, it would be in Twitch's best interest to showcase a variety of streams to a viewer so they stay on the platform longer.

My suggestion is that Twitch keep a log or history of a user's viewing activity. You can indicate a new stream as 1) a never-before-seen streamer or 2) a streamer the viewer has not watched within the past 6 months. If a user views a new streamer for 15+ minutes, you should offer a reward and maybe have an option that lets them consider following the streamer as well. You should keep a 15+ minute requirement for new streams because it would force viewers to give the new streams a real chance. A viewer won't be able to determine if they really like a stream or not if they don't watch it for a fair amount of time.

Twitch can also potentially make more money off this new viewer reward system too. For example, if a viewer ends up subscribing to a new streamer through the reward program, you can potentially take a higher cut of that subscription fee because Twitch basically marketed that new streamer to the subscriber. It's the same way OpenTable charges restaurants for dining reservations. Nowadays, restaurants can choose to pay anywhere from $1 to $5 per diner and OpenTable will market a restaurant heavily if the restaurant chooses to pay them more per cover.

Just my two cents. Thanks for reading! :)