To have an adequate reserve for financial opportunities and emergencies. To assure ourselves a comfortable retirement income for old age. There are various viewpoints on how to achieve these objectives. Some people do not want to risk their savings in non-guaranteed investments. Others don't mind a small risk.
Work expands to fill the time available.
Expenses rise to meet income. The more complex, the sooner dead. Application of these laws to your personal situation might go like this. Suppose you have a business or profession in which you have four employees. All are busy, according to Parkinson's first law.