I, too, have experienced this clapping:
1) many times on flights to hawaii.
2) many times on delayed flights during the holidays.
3) couple times on flights with a large group flying together.
3) one time, on a flight where the pilot was retiring and this was his last commercial landing.
for some odd reason, I always feel bad if I don't clap. ...
... SO NOW I MAKE SURE THAT I YELL, SHOUT, POUND FEET, CLAP AND WHISTLE AS LOUDLY AS I POSSIBLY CAN.
it feels good, if only for a moment.