Another feature of this is that if your primary PC crashes, which happens sometimes especially with some games, your stream doesn’t go down too. This is more important for streams with more viewers and longer runtimes, as restarting the stream drops all the AFK viewers who may still be contributing ad revenue (or just boosting active viewer count which has other flow on benefits too).

You can see this effect in long streamathons/subathons as twitch automatically kills long streams so you’ll see multiday streams get cut up either manually by streamers or automatically by twitch every 24h or so, and the viewer count drops significantly and takes quite some time (many hours) to recover.