Here's why:

* Salt is a neutral compound: Sodium chloride (NaCl) is a neutral salt, meaning it doesn't have acidic or basic properties. When dissolved in water, it dissociates into sodium ions (Na+) and chloride ions (Cl-) which don't react with water to form H+ or OH- ions.

* pH is determined by H+ ions: The pH scale measures the concentration of hydrogen ions (H+) in a solution. A lower pH indicates more H+ ions (acidic), and a higher pH indicates fewer H+ ions (basic).

* No change in H+ concentration: Because salt doesn't introduce any additional H+ or OH- ions, the pH of the water remains relatively unchanged.

However:

* Very concentrated salt solutions can slightly increase the pH: At extremely high concentrations, the dissociation of salt into ions can slightly shift the equilibrium of water, leading to a very small increase in pH. But this is usually negligible in everyday scenarios.

* Impurities in salt can affect pH: If the salt contains impurities, like calcium carbonate, which is basic, it could slightly raise the pH. However, commercially available table salt is highly purified and unlikely to have significant impurities.

In conclusion: Adding salt to water typically has a negligible effect on the pH level. It remains close to neutral.