In democratic countries the politicians care about how the expenditure looks to the public. People think that 5 billion dollars in welfare is a lot of money, so

In democratic countries the politicians care about how the expenditure looks to the public. People think that 5 billion dollars in welfare is a lot of money, so it's hard to spend more welfare. People do not think that 5 trillion dollars on "defense" is a lot of money, so it's easy to spend more money on defense even though it has at best dubious return on investment.