Now I just though of something I encounter very often.
People who have played only D&D are most of the time are just bad players, and all the wrong naughty word D&D has teached them now needs to be beaten out of their heads! Even the most basic concepts of roleplaying need to be explained, and I always have to be sure that newbies I meet don't get their minds broken by D&D.
I've yet to see a veteran D&D player who can at least pass the most basic litmus test. "Your character is chasing the bad guy with a revolver in her hand. What you, as a player, would want to achieve?"
The correct answer is, "to figure out a way for my character to lose her revolver, so she can engage the bad guy in a fist fight, or maybe, so he would be able to escape!".
The D&D player answer is, "to shoot the bad guy, what else?!"