That’s one of my justifications / rationalizations of carrying the 5-ounce Sea-to-Summit 10-liter shower bag on group trips.  It saves trips to the stream / lake.  It makes a convenient dispenser of water in camp (although the platypus bag allows a higher flow).  It can be used to haul water for a dry camp.  In an emergency, it could be used to haul 2 gallons of fire-fighting water if a camp fire was slightly out of control (and eliminates any reason to not completely soak any campfire before leaving).  This is important up here because we have a lot of flammable ground and a fair number of human-caused fires are due to campers who start a fire highly on organic soil, unknowingly ignite the soil, and leave only to have a wind or time whip it into a blaze.  Also, in a heat-stroke emergency, it is far, far easier to bring 10 liters of water to the victim than to bring the victim to the water source.
But mostly, I like to take a shower every day or two.
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