I don't know if this has already been said but tap water in some areas in horrible. I wouldn't blame people from such areas buying bottled water, especially to make a good cup of tea.

The tap water in many places is just fine. When I worked in Huddersfield our new Managing Director (bit of a snob) asked me to procure water fountains and we bought water in. The water from the tap was far superior and just for cheek I filled a couple of the huge bottles with tap water. A good few people commented on the "improved" water from the fountains.