Well, they are growing grass, and many of those lots are fenced in. A garage could work as a barn/stable with relatively minor modifications. That's a pretty good scenario for small-scale livestock production. Fruit trees can also be planted - a little bit of compost & organic matter right in the planting hole will go a long ways. Once there is a good population of livestock in the area, composting can go into high gear, and then the topsoil built up to turn some of those lawns into productive gardens.

Do you have any idea how useless modern lawns are for growing anything other than that monoculture green carpet? Rebuilding a real soil system of any depth takes years. It's one reason I use raised beds instead of trying to til nearly dead lawn with only an inch or two of soil under it anyway.

Likewise with planting fruit trees. Most of my fruit trees are a few years away yet from providing any serious harvest though the orange tree may give me a few oranges this year.

This is not something that can be done instantly, overnight or via mail order and a Fedex shipment for tens of millions of people. Then there is the problem of learning your local environment, its pests, its growing season(s) and the oddities thereof.