When you do work, you are paying into the economy, providing goods and services for everyone else. When you spend your money, you are taking out of the economy, cashing out the value you deposited. When you hoard money, the economy has the benefit of the goods and services you provided to get that money but hasn't had to pay you out. You have invested in the economy as a whole at that point as your goods and services provide benefits to others that grows the economy as a whole. At some point, you spend that money and cash out the investment of the goods and service you provided.