Because evidently there is no way to differentiate that from a southern accent (according to their description of stating that someone with a midland accent could be from 'one of those big southern cities').
Though, I have noticed that especially here in Southeastern Virginia, accents of those of us native to the area differ greatly from Northern and Western Virginia. We have a tiny hit of a southern accent mixed with a tiny hint of an English accent, left over from colonial days.
And it's COKE! There is no soda, no pop, it's all coke! Unless one is trying to make a decision on which carbonated beverage to actually drink. Otherwise...regardless of the options, around here, you're going to be asked, "Do you want a coke?"