I read about this earlier today on /r/contentstrategist and they were saying that videos posted directly to Facebook get far, far more "plays" than if they are posted as links to YouTube. This is thanks to Facebook's AutoPlay for native videos, and whether people actually watch the videos more... Is not really interesting because plays/impressions is the metric by which a boss measures the marketing teams work, or how clients are billed.

So, this works because Facebook makes native content more prominent than linked content, which is filtered out.