Erik, While I agree that creating community gardens should be about facilitating gardening, for a couple of reasons I think its narrowing to consider only the reasons why individual gardeners garden as the benefits of community gardening. Certainly in a city like Madison, WI, where land to community garden is hard to find, making an argument for the support of community gardening on the part of the city or funders based on its recreational value, is weak.
Parkland accomodates more recreators.
Decision-makers and funders have many interests competing for their attention. They will most often make decisions to fund or support based on greatest good to the most people logic. Recreation, getting close to nature, getting your hands dirty, may be the best reasons to garden. They are not the best ways promote community gardening. Parks do all of that for more people.