I'm certain Netflix ran the numbers, and determined that a high-usage customer is the most valuable.
On "just ok" vs stuff actually enjoyable, "just ok" is fine until there is no better competitor for attention (e.g. a new smartphone game takes over the world). If they get to fit on the "actually enjoyable" scale instead, there is a better chance for people to keep their subscription, sometimes even if they end not viewing anything that month for whatever reason.
For instance how Netflix's catalog is attractive to new users/markets can be checked in regular polls, but it would be way more difficult to follow with fine granularity, far less precise, and ultimately a harder to handle number than just retention or number of new accounts.
This means Netflix could see decent growth on its numbers, good retention and a steady flow of new accounts created, while struggling to reach new markets where competitors are doing great.
This is an extreme example, but Blackberry typically had very good user retention and users loved their devices. Looking only at these numbers, they were doing fine for a long time (which is nothing to sneeze at)
The users who only watch a couple of things are the ones who are more likely to “get bored”, because in any given month there is a higher chance that there won't be any single thing they'd want to watch. Whereas someone who just does it regularly (say every day after work while eating dinner or w/e) is more likely to keep that habit.
[1] https://www.independent.co.uk/arts-entertainment/tv/news/net...