There is zero risk to a regulator in maintaining a pointless yet harmless regulation. There is nonzero risk to a regulator in revoking a regulation that may be

There is zero risk to a regulator in maintaining a pointless yet harmless regulation. There is nonzero risk to a regulator in revoking a regulation that may be blamed in the future by a crash investigator. Even if the risk is absolutely 0.0001% -- fear and CYA wins. Our system of regulation and collective transfer of responsibility to regulators ensures that like a federal subsidy, nonsensical regulations are forever.