Like stated previously, we've full-timed for 16+ years and have always used our fresh water tank for our drinking water along with everything else.
We travel constantly - moving around the country. Our first choice of a RV site is always a public park - national, state, national forest, COE, county, city. We fill our tank at those places. We have never sanitized our tank.
However, we do use two filters. People say that they don't trust campground water. Don't they realize that many people drink that campground water, including the employees? You have never seen headlines of hundreds of people getting sick from campground water.
We have volunteered in public parks and do know that the water quality is checked regularly. Why would they take a risk of people getting sick? They don't.
Now taste of water can be a concern and a proper water filter will take care of that taste. But the water itself is not bad because of taste or color. Our last house 16 yr. ago had horrible iron water. It was orange and tasted awful. However, we got an iron filter to take care of the color and taste.
People tend to fall for the marketing gimmicks of companies...bottled water and now with all kinds of additives for taste and energy. They're just putting chemicals in the water and people drink it. Think about it.
Some National Parks are not even selling bottled water anymore because of the environment issues.
Yes, some remote campgrounds might have a sign recommending that you boil water first. The probable cause of this is because of outside contammination from animals, shallow wells or environmentals. However, this shows you that campgrounds are monitoring the water.
Here's a good RV water filter store that has lots of good information:
RV Water Filter Store