Reminds me of my friend Alfredo who was from South America would drive. I also saw the same behavior in Ecuador last summer. Car horns usage is the norm for all driving activities. They honk at everything all the time. It is odd to see coming from our culture of mostly honking when we are PO'd.
As for the topic, I've never been honked at and lord knows I've slowed enough traffic on winding uphill mountain climbs. Lucky so far I guess.