When my mother was growing up, the ice man delivered ice for the icebox; they didn't get mechanical refrigeration at home until after the war (and that was in a medium-large city.) If you drank milk, it didn't keep very long, and most people didn't have cars, so delivery made sense.
When I was growing up, milk companies still delivered in the suburbs, and some bakeries delivered, as well as a few more specialized products like potato chips. Most Americans didn't have two cars, and they tended to do large grocery shopping runs on Saturday. My mom learned to drive around 1960 so she could haul us to pre-school, and my dad carpooled to work; they probably got a second car in the late 60s, and they switched over to supermarket milk around 1970, and supermarkets were starting to have enough shelf space by the late 70s to carry more variety of products like potato chips than corner stores could.
If I had had kids, they would have grown up around the time of the internet boom. Webvan and Kozmo briefly delivered a wide variety of convenience foods (and weed