Basically Youtube instead of counting views via actual requests for the videos instead uses a separate call that essentially says “hey, someone watched this video”. All the ad blockers rather than use a hard coded list of URLs to block which would quickly go stale instead use one of a couple different 3rd party lists the most popular of which is EasyList. EasyList decided to block the URL that youtube uses to register views on the principal that it was a privacy violation because it not only registers “hey someone watched this” but also captures exactly who watched it which allows Google to track your viewing habits.