That's a good point, though, about the role country music (real country music) has played in the development of rock. Bob Dylan had something to say in a speech somewhere. I wrote it down I thought it was so important and here it is.
'The other half of rock 'n roll has got to be hillbilly. And that's a derogatory term, but it ought not be. That's a term that includes the Delmore Bros, Stanley Bros, Roscoe Holcomb, Gid Turner and the Skillet Lickers--groups like that. Moonshine gone berserk. Fast cars on dirt roads. That's the kind of combination that makes up rock 'n roll, and it can't be cooked up in a science laboratory or studio."
The Dylan quote says it...where did Elvis, Bill Haley, Ritchie Valens and others who helped move rock & roll mainstream come from? Their backgrounds included gospel, folk music, "hillbilly" music, etc. Add a smidge of blues, mix well, out comes rock & roll, which begat rock.