HB makes some good points, as usual. Personally, I've wanted to wear a helmet for over 20 years - I'm sure any 332 pilot with any imagination has spent some time in the cruise working out where those bolt heads were going to make contact in a hard impact! Or a 212 rotor brake, or harness guide etc etc. The biggest single aid to escaping a ditched helicopter (or burning one) is being conscious.
We have used STAS for 4 years now, and are about to start wearing helmets. Who knows what benefit there would have been for this unfortunate crew, but I hope we can move away from the "it might worry the passengers" mentality that seems to have prevailed for some time now.