State Farm uses payment signature for HIPAA disclosure authorization
At my pediatrician's office the norm is to sign forms without seeing them at all.  The receptionist has a computer screen; the patient has a signature pad with no display. They will say "please sign for permission to treat" then "please sign again for HIPAA approval" and so on.  I think you could ask to see the forms, but it would be breaking the social norms to do so.  You would instantly be a "difficult" patient.