Coke, Pepsi, does anyone really care?

OK, this is something that has long been a peeve of mine. And, I've always wondered if anyone has ever had a negative response. Server: May I take your drink order? Diner: I'll have a Coke please. Server: Is Pepsi OK? I mean I know folks have their preferences, but seriously has anyone ever changed their order based on that? Diner: Oh Pepsi, you don't have Coke? Not even a can in the back? Perhaps you could run over to the 7-11? No? Well I guess in that case I'll take a glass of tea instead.
I could maybe see 7-up or Sprite, just maybe. Definitely the Dr Pepper vs Mr Pibb, not even close in taste but Coke vs Pepsi. Sometimes I just say Coke or Pepsi, or whatever Cola ya got. The question just seems dumb to me.
Have a Coke and a Smile.