Why is it we don't plant urban gardens?

I was crossing the street the other day in Baltimore, by Johns Hopkins Hospital and I noticed that the city had hired landscapers to rake, cut, leaf blow, plant, mulch, and mow the center median. I wondered to myself, why not plant and cultivate herbs and vegetables instead of grass? Imagine how wonderful that would be?? I know there are a few urban cities that have begun this practice, it's time Bmore do it also! Perhaps then hospitals will provide and add whole foods to their patients instead of the processed, highly GM crap they now offer.... Which segues me into another story..... ((more on that later))