This seems to be a common refrain that Spotify can just "pull a Netflix." And this is very unlikely.
Firstly no matter how much opriginal content they could create, if they don't have back catalog it's going to be a total non-starter for the mainstream. A streaming service that has no Beatles, Pink Floyd, No Motown, No AC/DC etc is going to shed users pretty quickly.
Also music and movies occupy very different spaces in peoples lives - emotionally, socially, where and how they're consumed and shared etc.
People need music for their commute, for their workouts, for their parties, at bars and for their workdays. People only need movies when they're home or maybe stuck on an airplane.
Lastly Spotify needs to stay in the record label's good graces. If they were ever to be viewed as a competitor or a thread to any the big 3 record labels it would be reflected in punitive price increase when it came time to renegotiate their licensing deals.