The individual has little to no control over the water or pipes that runs the water to their home. It is a take it or leave it situation. If you own your home, then you might be able to install a water filtration system. This might be at the very least $200+. Okay. That doesn't compete with the price of bottled water. What about just a water filter pitcher? $30+. Well, now that's far more reasonable, but still represents 20-30 cases of water.
Bottled water IS the cheap, easy option. Should people fight and vote for infrastructure improvements so that they have clean, good tasting water? absolutely. But while we're working on that, we'll drink bottled water.