It is not the only one that matters, though it does make up (looked up, link at bottom) about 50% of federal tax revenue. Payroll taxes make up another 36%. Everyone who works and is paid aboveboard pays federal payroll taxes. It's only those whose AGI falls below whatever the present threshold is, or who are not paid aboveboard, who don't pay federal income taxes. If wages were keeping up better with inflation, we'd probably see a lot more people paying federal income taxes.

https://www.taxpolicycenter.org/briefing-book/what-are-sourc...