I think this is a very important point. These media companies have not been able to extract as much rent from their IP as they could ten years ago, and their shareholders are not happy about that. They absolutely have to try something.
Certain companies have been extraordinarily interested in implementing WebCrypto without mandating HTTPS. Which is to say, a man-in-the-middle attacker could trivially modify the JS that calls WebCrypto and cause different operations to be performed.
My suspicion is that they have contractual agreements with the non-technical folks in the studios that they have to "encrypt" content, and the technically-competent redistributor has no direct interest in the crypto being sound. If the API gave them 256-bit military-grade AES encryption, but only in ECB mode, they'd probably use it.