the reason is, like previously mentioned, blues players used it so the blues influenced rock players incorporated that into their music. But I think people need to use more than just one scale, gets reeeeaallly boring. you have to work in some major (other modes), Harmonic minor (yngwies stereotypical scale), and throw in something,"out there". like the Persian scale, cool east indian sounding (thats one of my personal favs to improvise and mess around in!).