How many people have never drank water from the tank?

Is there any guaranty that bottled water is any safer? Most decent campgrounds that I have been at are on city water. It is probably tested more frequently than bottled water. I always sanitize my tank and lines and filter my water.
If you were to see the buildup of crud in city water lines it would scare you. Why would the piping in a facility that bottles water be different?