> This is measured by the "diversity" of content consumed, which decreases if a user is their own recommender.
The recommender in the GP and OP is a video store clerk, that’s probably self selected into that kind of job by their special interest in movies
Additionally, studies have found that (when A/B testing recommender system vs no recommender system) users create their own, more localized "echo chambers" in absence of a recommender. This is measured by the "diversity" of content consumed, which decreases if a user is their own recommender.