In fact, I need permission from my manager's manager's manager in order to stay past 7pm.
This company believes in a strong work-life balance, and this is one of the ways it achieves this.
Also, it "changes the world" in good ways, not by "connecting people" through bogus data siphoning addiction traps.
Personally I strongly prefer no fixed working hours. If you want to work at night, so that you can do things when it’s light out (especially in winter), and you still get the expected results, what’s wrong with that?