The Property Site Visit by a trained, qualified Professional Appraiser of the Interior, Exterior & surroundings of the Property being used to secure a major amount of someone else's money in the form of a Mortgage loan IS the most important aspect of the Appraisal process. Items missed or left out of a "report" by an untrained, unlicensed & unregulated "Site Inspector", whether by mistake due to lack of training or deliberately in order to secure future work from the AMCs & GSEs , WILL affect the whole process and produce flawed Property Appraisal values.
Bundle enough of these flawed values into financial products sold to Investors and bingo - enter Great Recession #2, another bail out of FNMA/FHMC & Banks, and more Homeowners suffering Foreclosures and Retirees, Working Individuals and Pension Programs suffering substantial 401k, SEP, Pension Fund, etc, losses from which many do not have the years left to recover. In addition to another "lost" generation of future Homeowners like we are already experiencing.
The Property Site Visit is NOT the portion of the process in which to cut corners - ask any experienced Appraiser how many times what was described in a Listing &/or a phone conversation with an Owner or Agent turns out to not be the case once you have walked through and around the House & Property.