Also depends on where the watershed is from. Due to all the farm runoff out here, there are boil and do not drink advisories on all the local streams and creeks. The water here comes from a limestone capped aquifer that has won awards for its taste and treatment. If you are above the tree line in Colorado, for example, with no animal waste entering the water, you are probably safe. The Ohio River is cleaning up, but still has to be treated with caution. Pollution is a real issue and for decades raw sewage was dumped into the streams and feeders. I live out of town, in a "city" of about 5K people. Our water is shit. As in it tastes, for lack of a better description, old. I filter everything to make it taste better. The pipes here are old and the water towers are from the 50's and probably need to be replaced. $.50 a gallon for bottled water is too expensive, but then again I am a cheap bastard and would rather spend $40 on a filter that gives me thousands of gallons.
I wouldn't even drink water untreated while hiking in Adirondack Park. It may be remote mountains, but all those hikers are peeing and pooping all over those woods (myself included). It's still very tasty water after running though a filter and adding purifying drops, but I always treat it. I think everyone does, at least everyone who thinks about such things.