Our current system relies on the economic externality of relying on private vehicles and private transportation on local infrastructure to artificially lower the transportation costs for grocery logistics. It’s much cheaper to run an 18-wheeler to a large grocery store on the edge of suburbia than running box trucks all over town. It doesn’t actually lower food costs, because people pay a large fraction of their income to that private transportation so that they can access that super-grocer, and then the grocer seems to jack up the price of food anyway.