Youtube has far shorter videos (5-15 minutes on average), defaults to 480p or less most of the time and the visitor session length is much less than the average Netflix stream.
Netflix is doing 720p / 1080p defaults on most players, 1 hour to who-knows-how-long non-stop sessions (I personally have binge-watched like half a season of TV shows in one sitting occasionally) and gets daily recurring traffic from multiple members per household.
