Gardening is intrinsically joyful and healthy.

Gardens produce one of the most important goods
for our sustenance: food!

Gardens are a central part of the circuit of resources: Organic waste goes back to the soil and produces new food. One of the fringe benefits is the reduction of household waste and the resulting need for expansive landfills (euphemism for "garbage dumps").

The garden provides a metaphor for the basic economic model of Adam Smith, Karl Marx, and David Ricardo: we create value by adding our labor to a resource (fertile land). The fruits of our labor can then get consumed by us or traded for other products. As our gardening gets more evolved we tend to specialize and increase our trades.

In gardens and agricultural land human expansion meets head on with nature as development encroaches on agricultural land, as pesticides collide with our striving for a healthy life, and in the conflict between ag industries and proponents of humaine animal treatment.

And, a quite essential function in my view, many gardens provide homes for fairies, gnoms and elves.