Because you couldn't pump water. They either died or you got them across the border where they could get something to eat and drink. You can live on dates for a while, but they're too sweet for a regular diet. It's a lot of work starting fires in grain fields, unless you use napalm from planes or helicopters. Even then, it takes a lot of napalm.
Fields are big places.
Yet fires were reported all over. It looked like the Depression in the thirties in the cattle country of the Southwest. Just skeletons of steers lying around. They wanted to destroy the food supplies. We drove 2,200 miles and even at that time I didn't see a single hospital that wasn't damaged.