The Culture Of Yoga

As my mind wandered off during yoga today, I started thinking; Why is yoga so popular? I also recently read Malcolm Gladwell's "The Tipping Point" which talks about why trends become trends. So I am wondering when, why and how did yoga tip? Why do people want to suffer so much and wear incredibly tight clothes? I plan on researching this and maybe even making it part of my senior project, because it really does interest me.