Yes, you're right that for home gardens composting is enough. However, we are able to sustain the current population -- most of whom is not engaged in farming -

Yes, you're right that for home gardens composting is enough. However, we are able to sustain the current population -- most of whom is not engaged in farming -- on the current arable land by intense agriculture. This means planting extremely hungry crops that produce high caloric foods. Your home garden is not intensively cultivated the way most farmland is. Yes, more people should garden. No one should think it's the end-all answer to our food problems, or even that it's going to make a huge difference. Still good to know where your food came from and some stuff tastes better.