I was customer facing back in the day in a nonairline business. I believe it is largely training. Just as a trivial example, it was drilled into us to thank the customer, and we did. It was reflexive. Nowadays I can't remember the last time I heard thank you from anybody. I thank them and they say, "No problem." Yeah, not appropriate. It's also the ever growing attitude that I (the customer service person) can be rude to you (the customer) if you are rude to me. Being graceful in the face of rudeness is a learned skill, but no one even trains people that an eye for an eye does not have a place in customer service. And adding to that, the consuming public treats customer service people (and pretty much anybody else) abominably. This does set up sort of a reflexive defensiveness that has to be consciously fought. But all this comes back to training. Management can help employees develop the ways of thinking necessary to be able to avoid going to work everyday and jumping over the counter to strangle the 10th rude customer before lunch. Which brings us to another problem I would guess plays a part. People working without breaks and meals. Virtually no one can even fake niceness if it's been too long since the last food, hydration, etc.