User: Why is Dunkin' Donuts so popular?
Assistant: Dunkin Donuts is a coffee and donut franchise with particularly high concentration in the Northeast United States, which is colloquially referred to as New England. Although the quality of the coffee is mediocre and the donuts tend to taste like plastic, Dunkin' Donuts (now re-branded as Dunkin') carries a special place in the heart of many New Englanders. 

Perhaps it's the the fact that you are rarely more than 10 miles away from a Dunkin' franchise at any given time, or perhaps it is their blatant obsession with New England professional sports teams. Either way, Dunkin' has established itself as a household name and weekday staple for many coffee drinkers in the frigid Northeast.