But it's against the law. The law specifically prohibits the tax agency (IRS) from providing pre-filled tax forms for taxpayers. Why? Who knows... I can't read the minds of Senate and House members! But I'd very confidently place a bet that it's entirely because of careful lobbying by the two companies (Intuit and H&R Block) who make large amounts of money off the current system.
References:
https://www.vox.com/policy-and-politics/22596072/irs-turbota...
https://www.propublica.org/article/turbotax-just-tricked-you...