It's not a matter of believing that all natural things are good for you--poison ivy, hornet stings... It is a thought pattern, not a logical belief. Meanwhile, there is something called the Lindy effect, which suggests that the longer something has been around, the longer it is likely to endure. People have been eating bread, eating meat, drinking wine forever, whereas stuff like high fructose corn syrup, artificial sweeteners, preservatives, are crap that could be killing us before we even know it.
Does that make more sense? We all have behaviors that are influenced by our subconscious, whether the subconscious is "correct" or not.
I'm calling myself out here. If I thought the above explanation was a good reason to drink excessively, I would not be on this site.