Why Does the United States Adjust the Welfare System to Allow

Why does the United States adjust the welfare system to allow certain benefits to persist for only certain periods of time?

A) Humans are fundamentally entitled only to a certain amount of government benefits.
B) Welfare service provision is easier to administer over shorter time periods.
C) Limited allowance of benefits minimizes the provision of public goods.
D) Limitations create incentives that make people prefer working to the low income they get from welfare.
E) Unavailability of welfare drives up wages.