There have been lots of studies that prove that North American tap water is tested more rigorously and is more safe to drink than bottled water. I wouldn't mind if people still chose to buy bottled water, except for the pollution caused by the millions of tons of plastic.
Time was, public places had drinking fountains. Now we must pay a buck or two for our sip of water - and then we toss the plastic bottle. Worse, people drink bottled water when they could just as easily drink tap water - at home, in the office, and so on. You don't need to filter it, and you don't need to buy it bottled. Just turn on the tap and enjoy. If your tap water has a chlorine taste, let it sit for half an hour.
This is one of the few areas where the Europeans have a worse record than North Americans in terms of polluting. On a recent trip to Germany I found that it was impossible to get a glass of tap water in a restaurant. When I complained of the waste I was told that it was no problem - the glass was recycled. But glass recycling is the most expensive and least efficient recycling there is, which means that most of the glass that is slated for recycling is diverted to the dump. And in any event, the fact that something is recycled does not make it magically non-polluting. A lot of energy goes into recycling, and a lot of waste results.
As an aside, here's an interesting bottled water story. When I lived in sub-Saharan Africa we had plenty of water but it was highly unsafe to drink and had to be both boiled and filtered. When I needed water away from home I bought bottled water. The cheapest brand of bottled water in Tanzania in 1997 came from the desert country of Saudi Arabia. I assumed it was produced by desalination of sea water. The label boasted that it was "Low Calorie!"