Biv, I know (knew) a woman who would say "not everybody" but it was her own uninformed fault. She went to great extremes to remove all sodium from her diet. Even to the point of washing any canned foods that she used. She was bragging about this one day. I told she needs some sodium to keep her cells healthy. Some weeks later I ran into her and she had been to the doctor feeling miserable. He asked her about salt and she started bragging - until he stopped her. Then he explained how sodium keeps body fluids in balance inside and outside the cells.
Viv, yes, there are a few exceptions, and this woman you knew is one of them. Someone who ate only unsalted plant foods could conceivably suffer from hyponatremia, which can be life-threatening. It could also happen to someone who works in a foundry or other high-heat area and hydrated only with water to replace copious water lost in sweating. Sports drinks tend to have electrolytes like sodium, potassium, magnesium, added to help those who are sweating heavily. (many actually don't have enough, so it's advisable to add some salted almonds, bananas, salted melon slices, or other electrolyte sources, along with the drink)
If you look at chlorine in the Periodic Table, you will see there are other elements in its column with similar chemical properties. Glad you are exploring this topic.