MJB,
Crash truck? Never heard of or seen such a thing. Good points though for any workplace where a fire extinguisher is required, just keep the cling wrap in it's box or it'll get filthy in a hangar.
Funnily enough I recently had a conversation with a CFI recently about this kind of thing and he quite liked the idea of protective clothing but was very shy about wearing a helmet with students.
I made the point that students tend to adopt the habits of their instructors, both good and bad. A student that starts training and progressively invests in appropriate safety equipment is more likely to have a preservative frame of mind than somebody who flits about in a jockstrap and stilletos.
I can see for an introductory flight it would be confronting for your instructor to wear a helmet, but the early lessons before hovering can be managed to be relatively low risk, barring mishandling at altitude and a helmet isn't going to help if you're mast bumping an R22.....
There was a fatal ground accident in Australia some time ago where the instructor left the aircraft and removed his helmet when outside the disk. He then returned to the aircraft while it was shutting down and was struck by a sailing blade at relatively low rpm. The injury was not immediately fatal, but the instructor never regained consciousness before succumbing. I believe the instructor's family posted on this forum at the time but haven't found the thread yet.