You do realize people have been showering/bathing for a very long time, certainly much much much longer than the convenience of indoor plumbing has been around. Why is this all of a sudden an issue?
People did a lot of things out of ignorance *including me!. It's just a part of responsible camping, pack it in pack it out, leave it better than you found it, etc
"Even biodegradable soaps, while free of harmful ingredients like parabens and phosphates that hurt wildlife and cause unnatural algae blooms, can damage natural ecosystems if used improperly. They can also affect water quality. (Just ask the guy filling up his water bottle downstream.)
There are a few things that can be done if you want to reduce your impact. Use all soaps sparingly when in the backcountry. Move at least 200 yards away from lakes, rivers and streams before using any soap. Dig a hole six to eight inches deep for dumping soapy water — the bacteria in soil break down the biodegradable ingredients. Pack out all packaging and waste."