Because it isn't exciting to the survivalist mind, in most cases. Aside from or not just limited to water supply, real world priorities can be experienced for training purposes in an extended power outage. It becomes obvious real quick that you spend a lot more time doing living chores than the things involving "sharp and pointy" things and guns. In cold weather environments, it only gets harder.So my question: why aren't more people flexing their creative (and functional) ways to preparing water?
In dire circumstances, people's standards will diminish with increased need.I suppose even urban streams are a viable source in a true emergency.
In Australia, in ordinary circumstances some people living outside of town have cistern systems for runoff rain collection. Toward the latter part of the dry season, sometimes the cisterns go empty and they have to summon a water truck for refill. Of course in a survivalist situation, the water trucks may not be available so I'm not sure what they'd do then.Rainwater is another matter. It's basically distilled by mother nature and is absolutely clean until it hits your collection surface.