I think the difference is the decrease in scarcity. There's a reason that intensive agriculture marks the beginning of what we consider civilization. Aside from the fact that it requires sedentary living, it removed the constant threat of starvation and relieved us of our basest instinct to kill or be killed. Human progress and arguably human evolution has gone beyond our genetic destiny and is now shaped by our works. People who live in first-world countries are unlikely to ever face a shortage of high-quality food, potable water, sanitation, basic medical care. There are simply fewer things to fight about.