IRS is great at sending letters but not so great at naming or publicizing things (see IRS Free File, or paper forms being available at post offices and libraries) or maintaining technology from this century (they send faxes regularly and still run COBOL)
Oh no they’ve always collected it themselves, you just have to wade through ~4K pages of tax code that has averaged one change a day for the last decade.
But if you get it wrong, they’ll happily mail you a correction if you erred low. Plus penalties and interest of course.
The middle men like Intuit are a symptom of the legislature trying to use taxes to incentivize or disincentivize every little thing and still get pork for their districts. There’s a good 20 pages of code and case law on the depreciably of race horses that I’m sure the Senators from Kentucky had a hand in.