"Idle chat" is important for safety.

- They need to work well together, and the better rapport they have with each other the better they're likely to perform in an actual incident. Regular interaction on the job is a part of that.

- They work a job that is often remarkably boring for much of the time. Drowsiness setting in is a real concern - a degree of social interaction is good at both keeping people engaged, and at helping them gauge how alert the other crew members are.