Capitalism and voluntary exchange would still exist too. Things would just be far more decentralized and locally controlled. That's the main reason, if alternatives existed, they would be hidden from the masses.

Yes, the movie goes into that specifically, and the technology is being used to maintain an empire. Certain people profit greatly from not revealing it, and it keeps their system of power in place.

There's other weird stuff too like how people at NASA say "we lost the technology" to go to the moon. Lost it? What the hell does that mean?! Why hasn't anyone been back? I have heard the Chinese plan a trip though...