The horn on a car can be used for lots of things. One reason to use it is to let someone know they are doing something wrong.
At Head St and Esquimalt Ave today the left turn lights were active. The truck in the left turn lane started to go, but a car in the opposing traffic also went straight through. They had a red. The driver of the truck patiently waited for the bonehead to completely blow through a red light before making their turn. I would have been laying on the horn at the person.
Another instance was a left turn at a time of day when it was not allowed. Bay St onto Tyee, you can turn left except between 4 and 5:30. One day around 5 a semi sat in the intersection blocking traffic, making a left turn. Nobody honked at him.
Come on people, these are perfectly good times to use that horn. Scare the crap out of the wrong do-ers.