Earlier quoted context omitted.
This would be nice, but they may not actually have all of the data: itemized deductions being one major missing piece.
They could. I envision a one time use token for each charity you give to. You give the charity the one time use token issues by the government, and they report your donation directly to the government. Financial institutions and other companies already give the government a copy of the form they give you for self employment income and taxable financial transactions. The states also report state taxes and property tax…
Or heck, let me just tell the charity my email address, and then tell the IRS that all the donations for that email should be credited to me. People who want more privacy can "just" sign up for bespoke email addresses.