When you have a lot, you have that nagging fear that someone will take it away.
Re your PS I'm pretty sure you'll find, on average, wealthy people live longer than poor people on account of better health care. I was going to say better diet, but probably being able to afford a personal trainer to work off that rich food is a more important factor.
Then again, you get people on a Mediterranean diet and lifestyle living into their 100s frequently and too rather humble living east Asians. They usually seem quite content too, probably the right balance.
The truly poor, I'm thinking Africa, south Asian and in general indigenous people living in ex-colonial lands, probably rarely live past their 40s.