Comment by jjcm

Hypothesis: There are two significant use cases you may not be considering, which make up a significant portion of YouTubes use cases:

1. Music, which often lends towards repeat content

2. Children as a demographic, which any parent will tell you will watch the exact same movie/show/video on repeat ad nauseam.

Because of these, it's likely that YouTube has found that repeats (in general) drive more engagement.