How many people have expenses and deductions that impact their taxes AND that the government doesn't know about? Something like 85% of people take the standard

How many people have expenses and deductions that impact their taxes AND that the government doesn't know about? Something like 85% of people take the standard deduction. I itemize most years, and pretty much everything I itemize (taxes and mortgage interest) are things the government already knows about. I think the only exception is charitable donations. It would be a great time saver to just get a form from the IRS saying "here's everything we know, edit any mistakes or things we missed".