Many people think that the inclusion of iodine is for support of the thyroid gland, and they'd be right, but most don't know why this is so important: iodine deficiency affects 2 billion people worldwide, and is the leading cause of preventable mental retardation.
A lot of health-food people shun iodized salt, but if they have children, they're putting them at risk, although it affects adults, too. Ideally, if you eat healthy, you should be able to get enough iodine in your diet, but that's only if the soil in which the food was grows is suitably rich in iodine. Most soils are nutrient-poor, as they've been repeatedly farmed for decades.
Iodine is also used by many other body functions.
Thus, it makes little sense to avoid taking advantage of iodized salt.