So, when you purchase a car with a 4 year, 60, 000 mile warranty, you don't expect to pay for oil changes? RainSoft systems are made in a state-of-the-art facility in Chicago, not by God.
You need to add salt to the brine tank (with any manufacturer's system), filters required changing (that's why they're called filters), and any mechanical component is subject to wear and tear, and potential failure requiring replacement.