Just because a food comes from nature doesn’t make it good..even if we want it to be. I think as humans, we flirt with danger perhaps to show it we’re in control. We can handle whatever it throws at us. We catch it’s poison fogs and put them in glass cases to mock. We steal snake venom to make anti-venom. We eat fancy foods like blowfish (which is naturally poisonous) and eat raw fish, and expect that we don’t end up sick or dead.
Who likes rhubarb pie? Rhubarb leaves are poisonous, raw or cooked, so instead we eat the stem. Many like Nutmeg, which contains myristicin, a substance that can cause hallucinations, convulsions, vomiting and worse. Eating cherry pits and apple seeds can cause cyanide poisoning in large amounts. See this link for more dangerous foods.
So why do we tease nature? Test the limits of our bodies? The best reason I can think of is: Because we can.