It seems more dealerships are charging for diagnostics rather than just doing what the owner tells them to. A couple, but far from all, around here will at least credit the diagnostic fee toward any repair that is done.
My guess is the policy is a result of idiot car owners coming in, telling the service writer what the problem is (because someone on a forum, their dad, or whoever told them so), only to have the repairs made and the problem still remains. The idiot car owner is pissed and blames the dealership even though it is the idiot car owner's fault.