I find it strange that Spotify is able to list almost any band and music out there, and streaming video providers not. They are even forced to create their own content. Seems that the music industry has a better separation between content creators and providers than the movie and series industry.
But you're right though, the difference is stark. I don't think I've ever had a random tune I'd like to hear come to mind and fail to find it on Spotify, conversely I can honestly say that I have not once found a movie I've gone looking for on either Netflix or Amazon Prime.