Because without salt the life of human beings and many animals is impossible.
"salt of the earth" means a valuable person. You'd never know it from modern society, but salt used to be a very valuable commodity.
Salt at one time in history was very valuable. It was so precious that they had salt cellars with tiny spoons to make sure no one took too much. Only the high table in the Middle Ages had salt, so anyone who had salt to trade had an valued item.
It was a long time ago in africa because it was used to preserve food, make it more tasty, and it replaced salt lost when they sweat. Salt being more valuable is an opinion though, but for west africans, salt seemed more valuable
i think salt, because in 1600 there were lots of trading going on and salt was valuable.
In the middle ages salt was very rare and valuable, so a person "worth their weight" was a person who was needed and valuable.
In the Middle Ages one of the most valuable items was salt. It was considered so special and valuable that only the nobility could use it and it was kept in small boxes with little spoons to use it.
salt
salt
SALT.
gold and salt .
Salt and gold.
Salt