I thought this was obvious. Surprised to see people talking about it here, although in retrospect it makes sense that people here find it curious. (When I saw snow for the first time at the age of 20 when I travelled to America, I was mesmerized and stared at it like an idiot).

Coconuts are heavy, and if it falls on your head you'll probably die, or atleast have heavy injuries. As kids it was drilled down to us never to stand underneath coconut trees.

Also sometimes they fall in clusters, like 3 or 4 coconuts would fall down simultaneously.

Don't park your car under coconut or jackfruit trees. I personally know plenty of cases where windshields have been smashed by falling coconuts or jackfruits.