Why didn't the Sharecropper's cabin have a roof?

From Cold Coon and Collards: 

I rode in the cab of the pickup with Granddad to the Cooney’s sharecropper cabin. Their blackened and decrepit shack sported jagged holes in its sagging roof, and one room had no roof at all. A big black kettle hung by a chain from a rough timber tripod in the middle of the yard. Beneath the pot burned a few chunks of wood. A barefoot woman wearing a white apron over a faded print dress stirred the boiling laundry with a bleached and shaggy wooden rod.

One of my earliest and most vivid memories was the time, as a small boy, that Granddad took me with him to hire some help for the morning milking. The Cooneys lived across the pasture, and as-the-crow-flies, were our nearest neighbors. The dirt road was farther, but Granddad didn’t have to walk.

I had seen plenty of colored people in my five years, but had never seen where they lived. I’d always assumed that they lived in tidy farmhouses like my family and relatives. The Cooney’s cabin frightened me. Was this all right? I stayed in the truck as Granddad shared Chewing tobacco with Alec Cooney, the head of the family. 

Over the next few years, I would get to know Alec, his grown son Robert, and Loretta, his latest wife. Occasionally one of the younger children would visit our farmhouse to play with me, and later, my little sister Polly.

I came to understand over the years that opportunities for sharecropper families had declined drastically during the fifties. Soon our family, who owned Sixty acres, got paid for not growing cotton, by the Soilbank, a federal program to support the price of produce. The sharecroppers had no work chopping pigweed out of the cotton rows. The farms that still grew cotton no longer hired cotton pickers, since the crop was harvested by a machine that stripped the bolls of cotton from the plants, and blew them into a chicken-wire trailer towed behind.

With no cultivation or picking wages coming in, and no acreage or livestock to work, families like the Cooneys fell upon hard times. Granddad’s offer of work was welcomed. Maybe Alec would be able to re-roof his house.

It must have been pretty miserable for the family when it rained all night, or when it snowed, which happened every winter. I doubt that Alec or Loretta planned on living a life this difficult, but they had known little else since they were born black and poor, ten miles from the nearest paved road.

When I wrote my memoir, I was surprised at the number of scenes which came back to me that involved segregation and racial prejudice. The deep south was still locked in segregation and I wondered why white folks spoke so poorly of their black brethren.

You can see how I tried to deal with the situation in Cold Coon and Collards.