I don't think it is common, plenty of rich folks out there who do just fine.
We just hear about the bad ones.
I grew up in a smaller town in the midwest. There were some neighbors, bunch of old guy friends living in post WWII era baby boomer houses just down a few blocks. Nice guys, they were small town attorneys, politicians, small businessmen who ran some very humble businesses, and etc. They all drove 10 year old basic cars, golfed together on men's night, mowed their own lawns until they couldn't anymore.
It wasn't until I was older that I realized that they were all on the board of a local community bank that they started long ago. Over the years the bank grew, absorbed other banks.
Everyone of them was worth somewhere in the dozens of millions of dollars.
In the US, there are 800 billionaires. There are 5.5 million people that millionaires by liquid assets alone, and at least another 17 million by net value from things like retirement accounts or home value.
Odds are pretty decent you know one of them, or know someone who does, and probably don't even realize it.
I think it's because there's nothing left to do except amass more money and power. Like most billionaires can do whatever they want, but they keep working, or are in the public eye. Why?
Why is this so common?