I saw this on Reddit today. If you google search (movie title) site:drive.google.com you can often find movies hosted on people's google drives and stream them directly.
I mean... it's shady but it does actually work. I tried it with The Martian (which I already own) just out of curiosity and it worked. Can be handy for those instances where you want to see a certain scene or line or something, but the 2 or 3 or 12 streaming services you subscribe to don't have it.