Where I live everyone is required by law to wear a helmet.
Even adults? You're in Australia, I presume. Is that a local, state or nationwide law?
A bicycle is not a motorcycle. Usually it's a lot slower, for one thing. And if you have a mishap and fall, you're more likely to fracture a wrist bone than to slam your head against the pavement. I know because I've had my share of bicycle accidents.
Just more nanny-state meddling, IMHO. Next thing they'll require all pedestrians to wear elbow and knee pads.