In the Cincinnati area, it seems like the restaurants serving different types of cuisines are not distributed very evenly. There is clustering of sorts going on. For example, take BBQ and New York style pizza.
BBQ seems to be concentrated in a corridor along Hamilton Avenue, stretching from Mount Healthy in the south to Fairfield in the north. There's Goodies (which I've yet to visit) and Pit-to-Plate in Mount Healthy, Big Art's about a mile west, and the Butt Shack at the north end.
New York style pizzerias seem to be concentrated along the Montgomery Road corridor, with a jog northwest to Mason. There's Aponte's in Mason (technically a New Jersey style place), then the Flying Pizza at Fields Ertel and Montgomery in Symmes Township, and Brooklyn Pizza and Pasta in on Montgomery Road in Montgomery. Add to that the pizzerias that serve a somewhat similar style in that area, and it gets even more concentrated. There's Pomodori's in Montgomery, a block east of Montgomery Road, and two locations of Cincinnati-based chain Dewey's Pizza, in Symmes Township and in Kenwood. Then there's the four chains of fast casual pizzerias that seem to offer pizza in a semi-NY style, all of which presently seem concentrated along Montgomery Road or Mason-Montgomery Road: one Blaze Pizza, two Pizzeria Locales, two Rapid Fired Pizzas, and a Cucinova. There's even an interesting place called Pizza Tower. Most of the pizzeria's that aren't big national chain pizzerias or a Cincinnati-style* pizzeria like LaRosa's seems concentrated in that corridor
This is not to say that there aren't other BBQ places or New York style pizzerias - but there does seem to be some sort of odd clustering going on. There's a much smaller secondary cluster of pizzerias near the campus of the University of Cincinnati, and the Five Burroughs pizzeria is far from both. The most famous BBQ joint in the Cincinnati area is the Montgomery Inn, in Montgomery, not the small mom-and-pop places on or near Hamilton Avenue. But there definitely seems to be clustering. No clue why. Population density doesn't seem to be it. Maybe cultural factors? Just a random musing.
* Cincinnati-style pizza seems to be in the style of LaRosa's, a 60+ year old local chain. The crust tends to be thicker and firmer than New York style, and it is topped with provolone rather than mozzarella.