It's marketing, all marketing. And bottled water may be hazardous to your dental health.
I can't name any studies off the top of my head, but it's been stated quite a few times in recent years that tooth decay is on the rise again in children. It's because more and more kids are being given nothing but bottled water, which may not have the funny taste of the tap water, but it also hasn't been fluoridated.
If your local tap water is that vile, or if you're simply concerned, do your teeth (and those of your kids, if you have any) a favor and get a high-quality filter installed on your kitchen faucet. Overall, it's a lot less expensive than continually buying bottled water1, and you're not creating more of a disposal/recycling problem with all of your empties.
1 A $50 screw-on filter will treat 80 or so gallons, or 250 liters, and the replacement cartridges cost even less. Where I live, you can't find a liter of bottled water for less than $1.19, and it's usually more. Do the math.