Even today we appreciate some food preserved in salt. Every year for decades my grandfather, and now my father would buy hundreds of hams and cure them for sale throughout the year. Hundreds of pounds of salt are mixed with sugar and other spices and carefully rubbed into the meat. After repeated applications over several weeks, the ham is hung up until ready to be consumed. The salt penetrates the meat and keeps it from spoiling.
Salt is essential for life.
In the Middle Ages there were two kingdoms in West Africa, one which possessed gold mines, and the other which possessed salt mines. There was a flourishing trade between them, because the second desired gold, but the first could not survive without salt. Salt is so valuable, in Roman times the soldiers were even paid with it. The big concern, however, was to get pure salt. Salt is easily confused with sand, and sand is worthless.