In the same way that online advertising needs to display millions of ads to reach only hundreds of people, the recommendation system may not be intended to work at 100% efficiency.

YouTube "recommendations" work as far as I can tell. If you take two people searching for some subject area on YouTube, and only one of them knows how to search past the initial "popular" recommendations, each person will produce very different results.

If neither person is a skilled searcher (most people are not), they both end up with the same results. Those videos receive thus more and more views. Videos with millions of views help Google sell online ad services. If views were distributed more evenly across all videos, would that make advertisers more interested or less interested.

What's the point of a recommendation system that does not recommend a new video in the same category. To promote certain videos to attract large audiences and thus draw more interest from potential advertisers. More advertisers bidding on fewer popular videos would seem to favour higher prices paid to Google.

Some of the best videos I have seen on YouTube have less than 500 views, some even in the single digits. I found them through automated searches, not "recommendations".

Google makes information accessible with the belief that relevance is directly proportional to popularity. The company was founded on this idea.