I think it's a bit naive approach. The food is cheap because of the highly efficent agriculture. If you are going to grow stuff yourself your output per square meter is probably going to be much lower and it's going to take a lot of time and energy than if you were to rely on the economy. It's simply not feasible for masses to go back, without changing their diet, ie having to eat less with smaller variety of food. And if you take into account the impact on the country's economy due to this shift, it would be disastrous and put your country behind every other country in the world. It would also mean that you were going to be exposed militarily because of the inferior war technology caused by the inefficient economy. And so on.