A very good question. I suspect a combination of social stigma and changing religious beliefs are at work.
Plus, while I acknowledge that the average westerner today lives a comparatively comfortable life of luxury compared to people in the past - but our lives are more complex and stressful than ever before. People have lived through wars and through social and political upheaval before, and disparity of wealth and social immobility have been problems throughout history.
Along the same lines of what @InTheAirTonight said, I think the extremely rapid pace of progress in the past 50 years is a big part of it. People's everyday lives have become starkly far-removed from that of our ancestors. I'm not a biological fundamentalist, but ultimately we are just animals and we have needs that modern living doesnt necessarily meet. To flip this argument on its head, consider plucking a lion out of the jungle (btw 'king of the jungle' is dumb, because Lions dont live in jungles!) and picture it trying to survive as a first-class citizen in the city - it wouldn't have enough skills or qualifications to get a job, nor even the basic literacy needed to fill-in the paperwork to claim social welfare.
Human society is crazy-complicated. For example, increasing rates of basic literacy and education are undeniably a good thing, but young people these days need higher educations just to qualify for entry-level jobs.
Plus, I'm not saying the answer is to revert to agrarianism or to reject progress - we just need to *collectively* acknowledge that society is broken.
