"Things are better than they've ever been, on average."
Sure but that isn't how human psychology works. Especially in rich countries, where basic needs are met, inequality start playing a much greater role with respect to happiness.
Inequality has always been an important factor. The poor in France probably had it better than people in the stone age or medieval times when they made their revolution. Some can be said for the Russians. But they all made revolutions due to the high level of inequality.
If you look at countries experiencing big revolutions it seems to me to have not been about how poor or rich the countries were in absolute terms but rather how unequal they were. In fact in exceptionally poor countries you don't get any revolutions at all because people are to busy just surviving, and there is no intellectual class to advocate it and fuel the flames.
Also "better" is a tricky term. Every society place different expectations on people's lifestyles. One interesting thing I observed about America e.g. is that if you look at things purely statistically in terms on material goods you'll find that the Americans has more TVs, bigger house, more and bigger cars, more of all sorts of stuff, go out eating more frequently etc than say your average Scandinavian or Dutch person. Yet interestingly when you talk to these Americans life seems much harder. They worry about having enough money to repair their car if it breaks down. They need to go to work or whatever. They worry about not being properly covered on medical insurance, not having enough money for their kids college. They seem terrified of losing their job, or getting one will less good health insurance or whatever because they have a particular condition which requires this or that particular insurance which only the particular job they have now provides. So many seem overworked and stressed out.
In comparison, I don't even have a car, and it isn't a big deal. I go to work on a subway. My dutch friends would often just have biked. College education, no worries already taken care of by government. Health insurance. Same deal. Worried about losing job. Not a big deal, my work doesn't have any special perks I need and unemployment benefits are quite good so I will manage fine until I find a new job.
It seems American society has manage to create this system where the only acceptable lifestyle for a normal person is simply far more expensive than most can afford and they borrow money to keep up appearances. While in most of Europe you can be happy with a lot less. The really important things in life are taken care of like health, school, work etc.
Having smaller houses, cars and fewer huge flatscreen TVs seem like a small disadvantage in comparison.
I am not saying one thing is better. If American truly just want lots of stuff, maybe that is the best approach, but it just doesn't seem to make people that happy or calm to me.