Not entirely true, you forgot that if they turn to the dark side and guarantee values through comp searches, make issues "disappear", and become an advocate for the loan officer, they will be well paid and busy too.
For those who do not have a stable of Non-lender type clients to provide orders, the choice is becoming work fast and for peanuts or bend and break the rules to make the client happy. When AMC's control so much of the market for potential orders they can drive down the fees, After all, all filled in forms are equal to them.
The fee appraiser business model for success using low paying AMC jobs is quite simple really. Hire several trainees to do the work, pay them 40%, sign off that you (supervisor) inspected. Very simple, nobody will check anyway. Nobody really cares. I believe that is why the big "E" prefers vendors with over 25 appraisers on staff.