I might agree with you, but these same people were all talking up a storm with each other in the gate area in ear shot of everyone...but became silent on the plane.
I saw a group of 7 college students who were loudly talking, laughing and goofing around in the gate area but became completely silent once they got on the plane and pulled out their devices...even though they were all sitting together.
The psychology of the behavior was astonishing to witness.