Helmets are required around construction sites for health and safety. That's not an argument to require helmets for pedestrians. Any particular activity can be particularly dangerous, and you can mandate safety gear for that activity, but that has absolutely no bearing on stuff outside of that activity.
And I agree that MHL laws should be more flexible, and not just a blanket "you must wear a helmet at all times while on a bicycle" statement, which is what it is in Australia.
