So it's time to file taxes in the United States and it occurred to me that I have to provide a lot of information that the government already knows. For instance, I have to provide the contents of my W-2 form, but my employer already sent the Internal Revenue Service a copy of that document.

Why doesn't the IRS just send me a "bill" for the taxes that I owe? In other words, why doesn't the IRS just save me the trouble of submitting information it already has and just tell me what I owe?

Obviously, there is some information I would still need to fill out, like self-employment income. But wouldn't it be easier, and save more money for everyone, to just have the IRS tell me the information it knows and, if I don't have any corrections or additional information that I need to report, just ask me to write a check and send it back?

EDIT: I'm interested in the political rationale for the IRS not doing this. As some commenters have noted, countries in Europe already have a system very similar to this where the IRS-equivalent discloses their known information and the individual fills in unknown information (such as self-employment income), so I am aware that it is technically feasible.