Duty of care, surely?
As an ATCO who has worked at a couple of GA aerodromes in class G airspace, I have myself, very occasionally, asked a customer "Gxx, the reported met visabilty is xxxm, which is below the minima for vfr flight, report your intentions". This is not to intimidate a pilot, or "police" the situation, it is to remind the (sometimes) inexperienced or (occasionally) overconfident aircrew of both the current weather and the vfr limitations. Just part of the duty of care and the purpose of the service; hopefully safe, orderly and expeditous! In this litigous world of ours, should anything happen to an unfortunate or unwary customer who got themselves into situation beyond their capabilties and I had not done everything I could to help protect their safety, then I would both feel and probably be held partly resonsible.