We often hear that salt was worth as much as gold once. But I also heard that Israel was a useless territory to empires back then. So if that's the case why didn't people take advantage of the abundance of salt there?
I don't know about in ancient times, but in modern times many of the waters of the Dead Sea are high enough in sulfates that it often imparts an unpleasant sulfurous taste to the resultant evaporites.
Additonally, the mineral content of the waters of the Dead Sea is very different from that of ocean water. The mineral salts in ocean water is usually around 85% sodium chloride, which is what ordinary table salt is made of. In contrast, the mineral salts of the Dead Sea are around 50% magnesium, and usually less than 30% sodium salts. Also, the Dead Sea has a large amount of bromine instead of chlorine, compared to ocean water.
Source: this textbook page (https://www.bjupress.com/resources/pdfs/science/chemistry/c12-in-depth-look-dead-sea.pdf), my own recollections.