(Not OP) I can think of many ways where optimizing for greater watch time is unaligned and often opposite to making me happy and giving me what I want. In the case of Netflix, what I want might be to watch one show at a time for one or two hours every night. It may even for some people be about watching The Office or Friends, a show they know well and just watch for comfort. What Netflix wants is for me to start a completely new show (and probably one they produced themselves) every single time I open Netflix, and also to binge watch for six hours every night because I have “so many shows to keep up with.” This may not make me happy. But they suppose maybe it’ll make me more likely to keep my subscription.