The purpose of government budgets is to control spending. That's why the president and congress fight so hard to assert that control over federal agencies. Budgets also serve another purpose -- as a pie chart of governmental priorities. When the government spends tens times as much on defense as on education, that has consequences. When interest on our debt is 3% of federal spending, and likely to surge in the coming years, that limits everything else that government can do.
The American people pay their taxes, but they don't really follow where their money goes. They hear a lot they don't like about "foreign aid" and assume that it must be a huge slice of the budget, far more than the actual 1%. A recent survey showed this general lack of knowledge, with 60% of the respondents saying that international assistance is at least 6-10% of the budget or higher.
On the other hand, the answers on defense and Medicare and Medicaid were much closer to the mark. Take a look.