People who CAN play usually pick something else. These songs mentioned there are the learning material of n00bs (myself included).

Hearing n00bs butchering these nice songs over and over and over again can make the shop guys really desperate. Especially the ones into classic hard rock (rather than metal or other).
I can see the news headlines: "Shop guy lethally injured a kid customer when he repeatedly smashed a vintage Strat onto the kid's head. Reports say the cops found the shop guy still foaming over the body and muttering through his clenched teeth 'not ever again...' "

Everytime i see or hear stairway to heaven it always makes me think of this clip from wayne's world

funny we are on the subject,,,,, this happends to be my sig,,,,, weird.

Actually, I think Hollywood may have gotten that from some music stores, as I remember seeing a sign similar to that in a local shop back in the late 80's. It was hand written, but funny at the same time. I knew the owner very well and he couldn't stand hearing it anymore. Everytime someone came into the shop to try out a guitar I guess that's what they played. He finally put up the sign. He was comical but would never complain if someone came in and played it. He would throw me out though because I would go in and play it knowing the sign was there LOL.

in high school kids would bring their guitars and play stairway to heaven or sweet child of mine. I'll never know why they didn't learn any other songs

I remember seeing a sign that said no seven nation army.