The amount of taxes being collected throughout the year are by design higher than what you actually owe to the government. That's the same in most countries.

Of course you can get your overpaid taxes back by means of the tax return - but a lot of people don't have the money or time or knowledge to do that.

The overpaid money is to the government if requested back, an interest-free loan - if not requested back, a gift.

If the government would now tell the IRS to fill out the form for you - then there would be significantly less income - due to more accurate taxation.