There may not be humans or cattle around, but all sorts of wild animals defecate, urinate, procreate, etc. in water. Treat the water (boil, filter, pills, etc.) before using it and you'll be OK.
If I'm in an area where there aren't poison drops and where there is no human interference, I'll take the risk. Outdoor activities are inherently risky.
I've come close enough to dying in the outdoors in other ways that I'm not concerned about getting the small chance of getting the shits from drinking from a stream that I'm 99.9% sure is safe.
