Hi Umar,
According to some articles I have read, almost 30% of the world population has genetic markers that makes them susceptible to developing gluten intolerance. As the article points out, these DNA test kits are readily available in drug stores. So, it is possible that people who are finding out they have these markers are making the choice to go gluten free. I actually took the test last week and waiting for my results.
One reason for why many people have these glunten intolerance dna markers could be the fact that humans have not had wheat in their diet for very long (less than 10,000 years). After all, wheat has to be cultivated and milled; needing agricultural skills that humans developed around 7,000 years ago. In contrast, fruits, nuts, vegetables, lentils, beans and meat etc have probably been in our diet for hundreds of thousands of years. It might be interesting to note that according to some Islamic traditions, the forbidden fruit that got prophet Adam into trouble was wheat.
regards,
bob