This is actually a food safety measure.
The purpose of canning is to preserve food against spoilage by microbial action. The method of canning is to heat food to pasteurization -- that is, the combination of temperature and time that kills a sufficient percentage of microorganisms -- and to seal that food in an air-tight container with a minimum of oxygen, to discourage further growth.
If a canned food is liquid, one can just fill the can with it. If a canned food is in solid chunks, something else needs to take up that space. Water is the preferred substance to displace air inside the can. Sometimes it's brine, often it's a sugar syrup -- but water is the usual substance. Water is cheap, neutrally flavored, non-toxic, and most food is substantially made of water anyway.
Manufacturers will often add a carbohydrate stiffener, like calcium chloride, to help firm up the cell walls of plant material so that the food quality lasts longer. As a bonus, calcium chloride tastes "salty" but does not increase sodium content.