Some people work after retirement out of financial necessity, while others work because they want to stay active and make contributions to society. Other people work after retirement to experience new opportunities.
Financial reasons that people keep working after retirement include bigger Social Security benefits if they delay receiving payments until full retirement age. The payments are noticeably larger and make a substantial long-term difference. The principle is the same for 401ks and IRAs. Some people also keep working for the health insurance benefits. In some cases, retirees have inadequate savings or the value of their investments has declined, and they need to work to make up the shortfall.
Social, physical and emotional reasons include a desire to keep working to stay mentally alert. It promotes social interaction and gives many people a feeling of purpose and belonging. People who stay in the same jobs often do so simply because they love the work they do. Others pursue new opportunities they have always wanted to try. The flexibility of work after retirement is also appealing, with many people having their choice of full- or part-time work. Some people have always worked and cannot imagine a life in which they are not working.