Isn't it because it differs so much from movie streaming? On major music streaming platforms you can find most of the popular music artists. I don't have any numbers to back it, but my gut feeling tells me a-number-so-close-to-100 percent that it doesn't even matter anymore it may not be actually 100. Movies? You can't get Disney on Netflix, you can't get Apple on HBO, you can't get... you just can't. Imagine having Metallica on Netflix, Madonna on Apple, Beatles on Sony and Silent Poets on Amazon.