Even when you take the standard deduction, only had one job in one state for the tax year, and have no investments or other income (ie. the only way your taxes could be simpler is if you don’t have any income and someone else pays all your bills), it’s still complicated to file taxes manually. Many other developed countries will automatically calculate the most common scenarios for most taxpayers, and only people with unusual situations have to do any manual calculations (or pay a tax preparer).