Lawyers are the primary reason why Netflix is becoming less convenient, and by pure coincidence, lawyers will benefit from an increase in piracy.
Money talks.
It could also be that people are more willing to make platform purchasing decisions when it comes to video and game exclusivity but not music. This would lead to lower interest to buy exclusivity by the platforms, and thus having full market coverage is more economical for publisher.
For movies, you have to negotiate separately with every movie producer for every title.
In other words, to start a music service, you need money. To start a movie service, you need money and connections to every Hollywood studio.
Sure, there are three major music companies and six major film studios plus a bunch of major tv networks / distributors but it's still a long set of negotiations.
I think the difference is that the music companies understand the value of each service having ubiquitous access to every piece of music. UMG's decision to stop their artists agreeing exclusives with single platforms demonstrates this to some extent.
I wish the TV / movie would learn a thing or two from the music industry.