Just saw this online and thought this ought to stop people from pirating. That and it's bound to hurt streaming services. The ads might suck but if you're willing to pay for YouTube subscription, even that's solved.
I currently have Netflix and have no plans of paying for YouTube Red. This might change my mind though. :)
Link: https://www.techradar.com/news/youtube-has-started-adding-free-ad-supported-movies