Because the brain is the most complex item in the universe. There are no right/wrong answers, there are no black/white answers (and as much as I wish it had a "Shades of Grey") it doesn't. It is an infinite collection of colors and number combinations. What might work for you might not work for me and we both presented the same symptoms. To make an over simplistic statement, the best way to study these things is with identical twins because most everything is identical. Even in those cases with identical symptoms, oftentimes the solution is different. With this in mind it is very difficult to set up testing with control groups. Unfortunately the best we can hope for today is a trial and error approach to relieving symptoms, because that is what we do. We can alleviate a symptom, but if we don't know what caused the symptom, we can't find a cure.

Does this make any sense and does it answer your question?