but yeah, they do exist. Like, for example. my friends family owns a Mexican restaurant and his grandmother hand makes all the tamales and 24 kinds of amazing salsas.
Tho, outside the cultural norms (BBQ, Italian, Mexican, etc..), you would have to be around an ethic neighborhood to find a specific food type in a mom and pop style generally. Medium to Upscale ethnic is easier to find. I have a Brazilian steak house, Sushi,/Japanese, Thai, British (Kidding!), French, etc etc all close to me. Downtown (Chicago) it's obviously much more diverse and easier to find M&P places all over in various ethic varities.