We have very hard water where I live. The biggest disadvantage is the difficulty in keeping water areas clean. The hard water makes a discolored ring in the toilets and sinks. It stains the showers and washing machine. I do not use water softener, but I do have to use special products to clean these water areas. For instance, we constantly have to use some type of mineral dissolving cleaner to unclog the shower head. Soft water can often be often be found in marsh or beach areas. My father-in-law lives a few feet from the ocean and he definitely has soft water. When bathing in soft water, you will not need nearly as much soap. It is also not a good idea to drink soft water on a regular basis. It has a higher salt content and is lacking in many key minerals that we usually gain from drinking tap water.
Hard water is caused by dissolved minerals in the water. This typically occurs in areas where there is a lot of calcium or magnesium in the bedrock that the water moves through on its way into your well. There are simple chemical test kits that can tell you if your water is hard, but most people know because hard water tends to cause stains in sinks, bathtubs, and washing machines, and the minerals create buildup in water heaters, coffee makes, and in cookware. The main disadvantage is these deposits, which can be hard to remove completely.
Hard water has health benefits, because it provides minerals that we need to have in our diet. You can use a water softener in your house, but these need to be used carefully because many of them remove the hardness by a process called ion-exchange, which results in putting large amounts of sodium into the water instead; excess sodium consumption is not healthy, and can contribute to high blood pressure.