Studies have shown that an increasing number of retired Americans are choosing to return to work. The reason is normally not because they need money.
Most people dream of the day when they no longer must work for a living. After a long work life, they dream of being able to do other things with their time. It does not apply to everyone, but most people look forward to retirement.
We also tend to think that retired people stay retired. However, over the last couple of decades, studies have found that an increasing number of retired people decided to go back to work. One study concluded that 40% of working Americans over the age of 65 had previously retired.
It has often been assumed that retired people who return to work do so because they have no other choice and because they need the money for some reason or other. Nevertheless, most people who do return to work do so voluntarily as The New York Times reports in "Many Americans Try Retirement, Then Change Their Minds."
This trend might be the result of people living longer, healthier lives and work being less physically demanding. Another reason is that the new job is more flexible than the former job. That also suggests those who return to work are generally better off and do have the ability to make the choice.
People who have more money and who work in less physically-demanding jobs live longer and healthier lives than others. Retired people who might need to return to work because of a lack of money, might not be healthy enough to do so.
Reference: New York Times (March 30, 2018) "Many Americans Try Retirement, Then Change Their Minds."