Two other possible reasons:
1) Nail holes may cause leaks;
2) Completely unspoiled corrugated sheets retain their value longer.
I think laziness tends to be the father of innovation... look at the vacuum cleaner or the snow plough...
No Andy, they use nails and cinder block together. I lived and worked in guatemala when I was young. The idea is to use the two together. The blocks help prevent wind damage or so the thinking goes.
These brick appear as they are purchased, while many people put rocks on the roof or trash. If they could find something that is beautiful this roof would install very easy and fast.
I will try to walk over there and see if there is nail. I have seen these roof in many places without nails. Nails do cause leaks and rust in galvanized metals. I have installed many of these roofs on the farm, we used a special nail with rubber around the head.
The commenter about the using the two together appears to be right. You can clearly see two rows of nails in your picture; one at the top and another along the roof beam midway down the roof.
I guess you can see it, when I took the photo, I had to hold it up in the air and shoot. Forgot I had a photo...
Those bricks on the roof are annoying during earthquake: First the walls collapse, then, if you are still alive, you get trapped or killed under those bricks.
Thanks, good point on earthquakes.
I was in Jojgakarta, Indonesia within 5 day of an earhquake, the majority of people died because the red clay roofs fell on them.
clay roof tiles can be installed without using nails. There's a foam that perfectly sticks the tiles to the roof, and is even stronger for hurrican zones!