Stirred not shaken!

Why is it that every time I get an ice coffee from Dunkin Donuts, the person who gives me the coffee flips the cup upside down and shakes it for a few seconds? Is that supposed to somehow dissolve the three tea spoons of sugar stuck to the bottom? Really? How about you stop using granulated sugar and switch to, oh I don't know, simple syrup? Nah, that would probably make too much sense.
EDIT: I have just been called a dumbass because apparently Dunkin Donuts already offers "liquid sugar". If that is the case than why the fuck isn't it clearly advertised?