There is a class of rich people in the US who really like that people believe this. It allows them to spread a lot of fear about higher tax rates for high incomes.
Not to mention the influence of companies like Intuit, which has been pushing against convenience in tax filing for decades because its entire business model relies on people being unwilling or unable to file by themselves: https://www.propublica.org/article/inside-turbotax-20-year-f...