There are several purposes for the addition of sodium. Sodium content has a technical effect in the food. In fact, the amount of sodium or salt that can be present in dough to make bread, for example, is fundamental in order to give a particular characteristic to the bread. In fact, if you reduce sodium too much, you may end up with bread that is essentially not what consumers can expect to be bread. It affects the viscosity, if you will. There are also additions that are mandated by food safety. Sodium and salt actually contribute to the preservation of the food.
There are a number of additives, particularly for preservation purposes, where the salts used for the additive have to be sodium salts. There are several reasons why sodium is added. Of course, there is the flavour, which is essentially the palatability of the food and the acceptance of the food by consumers.
All of these elements are contributors to the challenges when somebody starts undertaking reduction efforts.