BZH, you're right that a lot of backcountry water is fairly safe, especially at higher elevations and far from agricultural and urban areas. But the Appalachian Trail hikers survey actually concluded that "For the most part, hikers treated their water. The less frequently they did so, the more likely they were to contract waterborne illnesses."

https://thetrek.co/appalachian-trail/top...f=embedded_post