It's a santiation issue. In a disaster, or personal emergency, managing the spread of disease, bacteria and viruses is a priority. If you are having a "disaster" or "personal emergency" that means that access to advanced health care is limited, or non-existent.

Most liquids require refridgeration after being opened to prevent the growth of bacteria. Yes, water in those little "water coolers" can be consumed warm because bacteria can't get up from the spot and into the bottle very easily. However, putting water into a bottle that held a substance that must be refridgerated at all times, is a bad idea. You'll never be able to adequately clean and disinfect the bottle, without contaiminating the water you put in it.