I am in part because I break out in an itchy rash when I eat it or accidentally get "glutened." It took me a long time to figure out what was going on, numerous visits to several doctors (several of whom TOTALLY misdiagnosed me, extending my suffering) until I, not a doctor figured it out. An allergist confirmed my suspicion, he was the 6th or 7th doctor I saw for this issue over a span of several months!
Since then, I have found that gluten is a very common cause of inflammation in your body and that inflammation is an underlying cause or somehow factors into numerous diseases. From my personal experience only after being off gluten, I have no more joint discomfort, no more dandruff, and higher energy levels.