Depending on which part of the country you’re in, the water may be hard. I remember growing up and visiting some relatives who had water so hard that I almost couldn’t get the soap to rinse off my skin. People in these types of areas have to use a water softener to get the water to the point where they can rinse soap off the skin in a normal way. Also, clothes washed in hard water turn out dingy, don’t look clean, and aren’t soft. Dishes washed in the dishwasher may have spots all over them. Again, people use water softeners so their laundry turns out clean looking and so their dishes look clean as well.
Note: One advantage (and maybe the only one) to having hard water is that people get a good amount of calcium and magnesium in their drinking water.