Because music streaming services compete (for the most part) based on experience and features not content. This happened after the market plummeted for music sales. TV and movies are still in the stage where everyone is competing with content by having exclusives while their services suck dick with few features, horrible UX, and ads. Im sure at some point they’ll go the route of music and games where youre not forced to sign up to a specific service to see a specific show, but who knows when that’ll happen.