Comment by HarHarVeryFunny

1) Because in the US your employer doesn't withhold tax at the correct rate - they withhold tax at whatever rate you tell them to (this is just a down payment). Places like banks don't withhold taxes at all. So, the US system forces everyone to file taxes (as long as your income is over some very minimal level).

2) Because in the US once your finances get remotely complex, filing taxes is a horrible experience, so most people are willing to either pay for someone else to do it for them, or for software like TurboTax to help do it themselves.