There are two reasons. Construction of the town began in the stone age. The Stone Age is a broad prehistoric period during which stone was widely used to make everything. The period lasted roughly 3.4 million years, and ended between 6000 BCE and 2000 BCE . 6000 BCE gets us into Biblical times and I can't comment on that except for metal things being made out of refined rocks. Big deal, still minerals, but they began an ascent toward industrial society that would threaten to deplete earth's natural resources in a mere 8 or 9 thousand years. Not so with the Stone-agers.
Stone-agers went 3.4 million years being very careful not to use up all the rocks. There are still rocks all over the place. I looked!
Keeping one's property intact while surrounding fields combine impulsively with oxygen drives one to compromise. We fear fire --one of the many disturbances to which humanity subjects itself. So I sneak out to our parameters with a product called Roundup® , without Norma's permission, and fight the field back a few feet. Yes, it is against my stone age Portuguese heritage but I must keep the property safe so that Norma may hear the seasonal pops of poppies and the howl of mating marigolds. And, of course, I have read the label and made sure Roundup® is made by the Monsanto Company.
Go in peace.