This is plain and simple laziness or more like convenience. Why do you put lawn on your back yard instead of a garden? Lawn is easier to maintain, just mow it every time it gets too long. A garden on the other hand takes time to maintain and you need to maintain it look after it to get a good produce. Now if you are all working from 8 am to 5 pm or 7 pm with overtime, what do you think is going to happen to your garden.
We had a garden in our backyard once, lots of tomato, spuds, beans and asian veges. That was possible because the missus was not working and she have the time to look after the garden making sure everything is healthy.
Trees are different story, because once a tree is fully grown not much maintenance and will give you fruit once or twice a year depending on the fruit tree
Some people do make it work. They go to their work come home and tend to their gardens.