There are a variety of reasons that people continue to work past what has been considered “retirement age”. Some people find that they are at the height of their skills, accumulated over a lifetime and are now ready to open the business of their dreams at age 70. While there is rampant ageism which excludes some very competent older people from the job market, lots of people over 65 are very innovative and undeterred, thereby bringing about the beginnings of a revolution in the work place..we’ll be seeing more and more 65-75 year olds going strong as experts in their fields.
Some people simply do not want to retire from the world..and miss community and feel they have so much to offer back to the world..and so take on jobs not so much for income but for social stimulation and continuation of belonging to a community and for feeling a sense of meaning in life.I have heard that many single women in their later years who want to remain in their houses/homes are investigating taking on boarders for money and for community. See House Share Service – Find Housemates with Silvernest
And there are some people who just have to work, to keep up their income and that is the main reason they stay on at their jobs.
You can find more information in a Washington Post article here.