you can just write a letter to the 3 companies (which are non-government too) and they will send you your report. That is essentially what these websites do on your behalf, just automate the process...
Annualcreditreport.com doesn't do it on your behalf. It guides you through the steps with each CRA so that you can get your free annual report that the law gives you. It's the only "official" site other than each agencies site. There are hundreds of others that often play on the users confusion/ ignorance. This is why I agree that AnnualCreditReport should be a .gov site to help it cut through the noise.