And can you use any salt for this purpose? I only see KCl and NaCl on the market. Do the other salts (CaI, MgBr, etc, etc) cost too much or have health effects, or do only the KCl and NaCl salts offer the flavor benefits?
most metal sals (e.g magnesium chloride) would taste too bitter or metallic, or chalky (in the case of many calcium salts), or else be insoluble or toxic.
Only sodium chloride (and too a lesser extent potassium) are have an acceptable taste and be non toxic.
Most other sodium salts (perhaps not sulfate/carbonate) would have some toxicity issues if taken in the gram scale every day
Monosodium Glutamate is a very commonly used food additive that (appart from tasting umami) enhances other flavours.
Salt is a basic nutritional requirement, by which I mean sodium chloride. You can’t live without it. We may have a need for trace amounts for other salts, but not as much as NaCl.
Because it is so essential we have a taste for it. We have this in common with most animals. Salt adds flavour to food because our taste buds are pre-conditioned to have a liking for it, because our bodies need it. Conversely too much salt is not good for our bodies, so we don’t like things too salty.
If other salts (or indeed any mineral or chemical at all) were as essential to our wellbeing you can be sure that our tastebuds would find them just as flavoursome, no matter how they taste.