I believe that has to do with shipping. The same way that grocery store tomatoes are varieties that can tolerate being shipped. People make choices. Most people chose not to grow their own food. Even a small lot can be used for a garden. In Little Italy in Ottawa, it is not uncommon to see the entire space in front of an apartment building used for tomatoes, beans, etc. instead of a lawn. There is square-foot gardening:
Square foot gardening - Wikipedia, the free encyclopedia
Corn may not be a crop one can grow easily without space, each stalk typically only produces one ear, although some will produce two, it does require garden space and because it is air pollinated, you have to plant it in squares to get pollenation. Then there are raccoons that will find it, as well as deer and other critters, but one can plant other "crops" instead of ornamental annuals.
My choice is to have a garden. It is a LOT of work, but well worth it. I also opt to plant edible plants (annuals) in my perennial flower beds--not all are edible, but many are--pansies, okra, herbs, egg plant, peppers, onions, garlic mixed in with the perennials.