I think it's a personal thing. I don't mind plain water (although I prefer ice in it) until I've gone through about 3 quarts in a day, then I want something a little different. Straight tap water is fine most places (although in L.A. it needs to be poured from one glass to another a few times to aerate it, and the sulfur water in southern LA is just nasty).
My wife, OTOH, will drink anything from a can or bottle as long as it's not plain water.