Because they are strongly tied; we are social animals. Are you saying for millions of years, our ancestors on average had lower quality of life than the developed world's poor?

It turns out electricity, air con, motor vehicles, and the internet are not the source of happiness, as much as advertising would like us to think otherwise. I bet your average homeless person in America would happily trade for a life in time past if it meant family, community, offspring, and the like. So much of our work today is meaningless, the same can't be said for our evolutionary history as apex predators.

Along many facets, yes, life is much better. But let's not pretend that we haven't regressed in many ways, for much of the population on Earth.

I'm measuring quality of life in terms of Maslow's hierarchy of needs here. For most of recorded history, the poor often lacked the absolute basics like water, food, clothing and/or shelter, and they continue to do so in many parts of the world. But in the developed world, these problems are largely solved, and issues of social belonging -- Maslow's third layer and above -- come to the fore.

The New Republic has a pithy way of putting this: money doesn't buy happiness, but poverty increases sadness. In other words, you may not be happy just because you have 3 square meals a day and a roof over your head, but you would be a lot less happy if you didn't.

https://newrepublic.com/article/120859/money-doesnt-buy-happ...

Social class is inseparable from quality of life.

80% of the hierarchy of needs is immaterial, so at best your argument is weak. In many cases people will actually sacrifice physiological needs to fulfill the spiritual, intellectual and social ones (flipping the need pyramid)