Helicopters, lots and lots and lots of moving parts all trying to part company with each other in a machine that keeps in the air by way of lots of thrashing metal. Hence as a heli pilot I try not to add any tension or stress to the situation but putside the machine I am as loopy as the rest.
In my experience heli's are like diggers and JCB's they are there to do a job as best they can, fixed wings are about moving large numbers of people from A to B, hence plank drivers are all about checklists and routes and plates and more anal stuff and heli pilots just want to get the job done then go down the pub.
I think the fact the in your average heli you sit with the pilot means he or she needs to display a certain calm and confidence so as not to worry the pax, in your cabin at the front a plank nobody can hear you scream.