It's even more basic than that. I'm convinced its just a matter of controlling food. Every major revolution in history is most commonly initiated because people were just starving to death. They had no choice, either die starving or die trying to overturn the system ... so many people opted to just try fighting because they knew they were going to die anyways. They literally fought for the next generation of people after them.

The dynamics are the same today but the ruling class know the lessons of the past so they control the food supply. They make food readily available and within the reach of everyone so no one ever truly is able to starve, at the very least no large segments of the population starves. This also isn't to say that everyone eats like kings either ... just enough food is made available and affordable to keep people from rioting. It's also the population at play too ... most of civilization will put up with shitty quality food, lack of food, low food supplies and inadequate food supplies for long periods of time before (or even if) they revolt.

It all doesn't mean that people are happy or content ... they just aren't starving ... as long as you keep them from starving, chances are high that they won't have enough motivation to want anything to change.