1) It's a great way to remind us of some great life lessons. Gardening is sometimes a microcosm of life. You have to practice perseverance, or your crop will wither and die. You must put in hard work, as the garden doesn't just plant itself. You must delay your gratification, as it takes months for the fruits of your labor (pun intended) to come to you. You learn to derive satisfaction out of small things. You connect the hard work it takes to tend and harvest the plants to the food on your dinner plate. God has more control of the outcome than you do.
I think that i've most appreciated the small amounts of sustained work that come with tending a garden. Being in a season of my life where I spend 12 hours a day engaged in intellectually exhausting work, I truly appreciate time every week to shut my brain off and let my hands do the work. Sometimes I literally have to stop myself from over-tending the garden, because I so enjoy the mindless labor that goes into working the soil.
I've also learned that I truly appreciate the small things in life a little bit better when gardening. When the difference between success and failure expresses itself in a nearly microscopic green bud (or even worse, no green bud, but green under the bark), it's easy to miss the signs. Forcing myself to slow down and observe the small things makes me appreciate those things all the more.
2) There's nothing more natural and local than your own backyard. I don't really find myself hopping on the food bandwagons. I'm not "organic-only", and I'm very skeptical of the anti-GMO movement. However, I can absolutely appreciate local, natural produce. It absolutely makes sense to me that when you're getting your apples from Chile, you're making a tradeoff. Either the apple is being bred for the best flavor, size, and quality, or it's being bred to make the trip to the supermarket without spoiling. Similar tradeoffs happen when you're mass farming. Either you can breed for taste and quality, or you can breed for other characteristics that increase yields at the expense of taste and quality. This isn't confined solely to breeding, but also extends to farming practices, transportation practices, and more. When you can walk into your backyard and pluck an apple off the tree with no concern of shipping it 3000 miles or having enough yield to offset farming costs, you can grow your apples in a way that is tasty and high quality, rather than compromising.
3) It has the potential to save huge sums of money. Just like any hobby or interest, you have to be really good at it to make decent money, but you don't have to be nearly as good to save a little money. This year I'm doing an experimental garden to see what grows the best in our climate and soil. Then, next year, I'll focus on what works, and see how much we can save by growing a bunch of the food that we can grow well. Will it save money? I sure hope so. Does it have to in order to justify the garden? I don't think so. However, once we start seeing the return from our crops, I think we'll be much happier to invest time and money into the garden.