One of the first European Rotorcraft forums (1979?) had a paper by the shrink that Schriener used for interviewing their pilots. I'll have to see if I can dig up my copy - basically he said that helicopter pilots were different because they operated away from the normally available support structure - air traffic control, runways, weather services etc. They had to make more independent decisions, were often the sole representatives of the company, etc.
Fascinating paper that helped to make why were are different a little more clear.