I used to wear one doing ag work but not for passenger work !! Wearing a helmet may make you feel safer but a) is that a good thing ? and b) If the pax then wear them that can create a danger ,as they will not be able to hear you give instructions ( if they are not connected or batt off say in a fire etc )
Lastly dont have too much faith in them ...the wearing of one actually caused the death of a friend of mine when the wire went around his neck .