As others have noted, the IRS doesn't know everything, and some things may be to your advantage to report to them. They could send you a bill and ask you to fix it, but many people wouldn't know where to look to find mistakes.
For example: RSUs and NQSOs (employee stock grants) are in my experience handled extremely poorly by default. If I have RSUs vest when the stock is worth $10 a share, then I pay income tax that year based on income of ($10 x share-count). If I sell those shares later on, my brokerage reports to the IRS either: unknown basis value or $0 basis value. The correct basis value is $10 per share. There's a spot in the tax forms where you can tell the IRS that you have the corrected basis, but if you don't do this, you will pay extra tax, and it's an easy one to miss, especially if you're just importing the 1099-B.
At tax time my brokerage does send me additional forms beyond the 1099-B that include the corrected basis values, so its not that they don't know the right value, they just don't give it to the IRS directly. I assume this is due to IRS/congress rules and not my brokerage being obnoxious.