No honk in Switzerland, some honk in Romania, all honk in India. There's no one rule to rule them all.

I've recently visited the southern US (Texas, Louisiana and such) and I was very surprised about the lack of honking. When I returned to Europe I've felt like in India.

I myself pretty much never honk. I understand honking makes sense on narrow bendy roads like in the mountains, where you need to alert the drivers behind the corner, but I don't see any other legitimate reasons to be honest.