Why do Texans talk like Hillbillies?

I'm not trying to funny, but the truth of the fact is, while I was there they always said "Ya'll" and everything with a heavy hillbilly accent. "Howdy Ya'll, how Ya'll doing" this was famous among Texans. Yeeee Haaaw. Ok, now I'm trying to be funny. But seriously, I wish they could hear themeselves.