Maryland has proudly required motorcyclists to wear helmets since 1992 (though, the law is not without its detractors, who try to repeal it at every opportunity).
This makes sense, of course: we require seatbelts, carseats and booster seats in cars, and the occupants there have two tons of steel to protect them other vehicles, trees, and the roadway. In a motorcycle accident, the sheer size and weight of any vehicle, compared to the slight size and weight of a motorcycle, can cause terrible injuries in what would otherwise be a minor impact. Motorcyclists are easily ejected from their bikes, and suffer a range of serious and permanent head injuries, if not death. There seems to me to be little difference between a motorcycle and a scooter or moped.