Looked at all my local guide books and only the new Vermont and Secret of the Notch have cover shots of climbers with helmets. All others including the new North Conway and Rumney guide books are of climbers without helmets.
I think that minors can make the difference between a cover shot and a danger.
The obligation to wear a helmet is, at my knowledge, stupid. There is no obligation when you know that some of my friends had a cerebral commotion because they felt without helmet, that a carabiner can slip of the hand of a climber high above in the cliff, etc. Young are not stupid, they don't want to be hurt...if they are teach correctly that danger exist and they have to take protection for themselves, in other term that it is not just a campaign to have more client or to bother the kids, they will, by themselves, be more secure.
I don't think that wearing a helmet will bring someone to be more intelligent if he is not able to be safe. In my opinion, parent must like that there child learn to see the danger and how to avoid it...more than to know that they have the obligation to wear an helmet.