I enjoy a "naked" head on road and wear a "shell" while off road.
No real science behind my choice, and can only see me changing my habit if presented with some evidence that in "practical" scenarios I would be more protected.
As a Scout leader, I do have to wear a helmet for all cycle activities through Scouts, which I don't object to, but do feel that some of the "education" (brain washing) the young people are taught (school, TV, media), gives them a false confidence that they are safe because they are wearing a helmet.
As several have said above, if you want to wear a helmet, then wear one. If you choose not to wear one then don't, but whatever you do, respect others choice.
Would suggest that getting the law on the use of cycle lights enforced needs enforcing before we add more laws for the Police to deal with??