We have discussed this topic in class and come up with some valid reasons why people may do this. I for one will occasionally flash my lights if I see a person driving with their lights off in the middle of the night. I believe the last reason that I will flash my light is to warn oncoming traffic of a speed trap ahead that they may not see or be aware of. He began pointing frantically and gesturing for me to go. Horn use is very rare around here, too.
Angry people gesture instead of honking.
Then the offender pretends he doesn't see the gestures and resumes talking on his phone. I've had three occasions to use my horn in the last week, though. Must be some kind of record for this area. I can also claim that here in Hawaii we do not use much of the horn. Only under unusual or dangerous circumstances is the horn used here.