Older workers blasted through another milestone recently.

The civilian labor force participation rate among people 65 and older stood at 20% in May, according to an analysis last month of U.S. Bureau of Labor Statistics data by advocacy group AARP.

That's up from just 10.8% a little more than a generation ago in 1985.

Still, with surveys showing more than two-thirds of baby boomers plan to work past traditional retirement age, the question becomes, is 20% too low?

Age discrimination, family caregiving needs and health concerns are blocking many people from continuing to work past traditional retirement age, but it's difficult to estimate what the numbers would be if those two hurdles were removed, said Jen Schramm of the AARP Public Policy Institute.

Most people working past age 65 are doing so for financial reasons, she said, but other factors play a significant role, too.

Earlier this year, Janet Dante, 73, shifted her full-time therapy practice in Bethesda, Md., so she could work three days instead of five. She had gone back to school at age 47 to obtain her professional credentials after spending several years raising children.

"Money wasn't the only consideration for me, but it was part of it," she said of her decision to start a new career at 50. "Now I'm afraid of retiring."

Though her husband is now retired and friends said it's great, she worries about not finding engaging pursuits. "For me, continuing to work keeps me in a much better place."

Here are a few other reasons to stay on the job:

Social Security. A lot of older workers took time out of the workforce and haven't reached the 35 years of work used to calculate benefits. Doing so now can replace some zeros in that calculation. Plus, each year you delay claiming benefits past full retirement age boosts your check by 8%.

Delaying withdrawals. If you have hit the number in your retirement accounts to trigger the retirement green light, working a year or two longer without starting withdrawals will allow you to create a cushion. And if markets plunge, trying to go back to work in a bad economy can be difficult.

Keeping a routine. One of the biggest reasons people cite for leaving work is to "give up the daily grind," long commutes and predetermined schedules. But having no plans can lead to loss of self-esteem. Replacing a sense of purpose is vital in retirement, so if you have not yet found yours, don't be too quick to give up what you have.

Janet Kidd Stewart writes for Tribune Content Agency.