For a long time, Pittsburgh was a crap food town. For one, you couldn't eat steel. For two, there was no vibrant ethnic scene, just a divide between, as Fuller put it, "really rich people who ate in private clubs, and their workers who cooked at home. Basically there was no middle-class dining."
The '70s brought a little bit of Thai and Indian food, some sushi in the '80s, but it was essentially a burgh of red sauce Italian restaurants, steakhouses, pierogies, and fries on sandwiches/salads. Then Big Burrito restaurant group came through in the '90s and raised the bar with locally sourced food (working with farmers), creatively designed restaurants, and a higher level of service. BB acted like a culinary finishing school/networking center for lots of chefs who went on to open their own places (Justin Severino, Kevin Sousa, etc.).