I feel beginners are satisfied with overall lower level instructors because beginners rate quality either based on the 'fun factor', how easily they appear to transmit step patters, or most common, because the belief that since the instructor appears to know so much more than them, that the instructor is 'good enough' and it appears that there is so much to learn from the instructor.
After a few months, though, most beginners drop out or become satisfied with the level they are at, and either drift into low commitment / low difficulty areas like group classes or Proam, as it appears to them that their step patterns (that are now in muscle memory) have made them dancers, and compared to the others they are surrounded by, that they are 'advanced'.
It's too bad, because even tho there is a longer road ahead that does not offer as immediate a result as what they have had in the past, it is MUCH more satisfying to learn technique, as this makes dancing feel entirely different and (IMHO) much more enjoyable.
The problem is, that good social coaches are not usually much more than that, and can't usually easily manage the transition from 'group classer' to 'student of dance'. Even when it's a local pro teaching a bronze foxtrot class, it's not the transitional coaching needed to (for instance) make the leader's posture an issue, or the follower's understanding of shape a consistency.
I think it's that intermediate coach that is what a beginner needs. Problem is, most beginners seem to stop at 'good enough for the social' levels.