Consistent quality and taste are two of the principle differences between bottled water and tap water. Quality is in every container of bottled water. It's consistent and it is inspected and monitored by governmental and private laboratories. The U.S. Environmental Protection Agency has reported that hundreds of tap water sources have failed to meet minimum standards. Another factor to consider is the distance tap water has to travel and what it goes through before it reaches the tap.
Taste is the other major reason people prefer bottled water versus tap water.
Chlorine is most often used to disinfect tap water. That can leave an aftertaste and lead to other problems. Cryptosporidium is a waterborne parasite that lives in animals and can be passed into the water through their waste. Cryptosporidium oocysts from animal wastes have been found in rivers, streams, lakes, reservoirs and many other types of surface water. For starters, bottled water companies are required to use approved sources.