I will say that I do drink just plain water, especially if I am thirsty and it's right from an ice cold spring. Yet after I have quaffed my thirst, for the remaining time until the next spring or fill up or during a meal, for me it's gotta be flavored. It's just more satisfying.
There have been many times that I'll drink something now and memories from the trail can flood my mind of the moments I drank that same flavor. Hell, just the aroma of the flavor can do that.