Many of us are in parts of the country that have little or no issues with water. We have plenty of it and, by in large, it is clean. There are other parts of the country that have moderate to severe water restrictions. In such areas there is a serious need to use your pool wisely so as not to waste water.
The University of Arizona has a web site dedicated to water conservation and has some excellent tips for saving water.
Their recommendations range from using a pool cover to using ice compensating technologies so you do not need to drain your pool in the winter.