A bit of history concerning the buying of cups of coffee while traveling, short local travel.
Dunkin Donuts is now ubiquitous in New England. Every numbered route has a Dunkin's about every mile or so in populated areas, it seems. They are sometimes nearly across the street from each other. It's decent coffee, but people who care deeply about comparing one coffee to another assure us it's nothing special. How, then, did it take over an entire region and begin to expand nationwide?
I've told you the main secret already. It's decent coffee. We forget how abysmal roadsidc and corner store and even restaurant take-out coffee was - always was - not so very long ago. Come to think of it, that was true of coffee at home as well. People made a pot of coffee, poured a cup, then put it on a burner all day. We are now sensitive enough to the taste that we know that after 30 minutes or so it starts to taste unattractive. But we used to stop for coffee and find that the last two cups in the pot were the rough chemical equivalent of ammonia, having sat there baking for hours.
"I can make you a fresh pot. It will only take a few minutes." they would sometimes say, but we seldom felt we could wait that long. We were going from here to there, in a hurry, and took what was already prepared. Some of us were also shy about putting the shopkeeper to that much trouble, having to waste a few cups of coffee by throwing them out. That's certainly an oversensitivity, as it is their job, after all.
Horrible, thick cups of coffee, sometimes lightened only with powdered creamer. Some places seemed to intentionally make it weak to start, so that it wouldn't get so "strong" so fast. Everyone had their limit of how bad it had to get before we wouldn't drink it, and my standards were lower than most.
Dunkin Donuts relied on advertising about how fresh the donuts were. Sing along, oldsters: "Fresh ev'ry four hours. Fresh ev'ry four hours!" and donuts are of course a wonderful thing. But I can still eat "stale" donuts that are five hours old easily (Hell, five days old isn't a problem), while I could never drink that gas station coffee again. The reliability of the coffee won us over. That is how all the fast food and chain restaurants win us over, BTW: reliability and a high minimum standard. If they do not exceed their own minimum standard often, at least they don't fall below it, either. (I have mentioned before that the international complaint and disdain for McDonalds is pure bunk and hypocrisy. They moved into places where the other restaurants didn't have clean restrooms or staff trained in hygienic food preparation. They served fried potatoes and inexpensive beef sandwiches quickly. You never found a little gem of a McDonalds hidden away in Sussex that you could brag about to your friends, but you knew what the hell you were getting. Locals, and in-country travelers, not Americans, keep them afloat, thank you very much.)
Back to the coffee - and now everyone, even the gas stations, has nice flavored coffees kept in thermal dispensers - and DD's. They got in first. They figured it out and established themselves as a tradition before other places even had the idea new. I think something similar happened with Tim Horton's in Canada. Canadians coming to America used to wail and moan that we didn't have Tim Horton's here. Oh, it's so much better than Dunkins. You just don't know. Well, I liked it alright when we traveled up to Moncton. Nice pastry selection, and usually conveniently located. A decent cup of coffee. But I also found that New Brunswick 2005 looked a lot like New Hampshire 1980 (Moncton, maybe 1965), with roadside coffee to match. If you weren't at a Tim Hortons, you were often looking at a very bad cup of coffee. That Canadian chain caught the same wave that DD's did in New England. If you go anywhere else, you're taking a big chance on that coffee. Better keep driving.
Plus, they would go heavy on the sugar - an extra trick to convince you how much more wonderful it was. They've gotten pretty clever with the pastry and food choices as well, adjusting to the market rapidly. Steak and egg sandwich now, plus a fascinating collection of summer beverages, coffee or sweet fruit iced drinks. It's a tradition. You feel like a real New Englander every time you go.