sodium lauryl sulfate aka sodium dodecyl sulfate aka sodium laureth sulfate is cheap, readily synthesized and effective as a surfactant at low concentrations. Also, it is biodegradable, and the original source is organic (though now it is all synthetic afaik). This means it is in virtually everything that needs a surfactant/detergent. It lathers well, too. BECAUSE it is highly effective as a degreaser, people with dry skin, or skin that is stripped easily, or who wash/shower more than strictly necessary (yes everyone's needs are different, I mean more that they should for their skin type) will experience drying to some degree as the natural body oils are stripped from the interior of the skin, not just the surface. These people need a milder detergent, or to wash less, or to replace the skin oil with something else. Olive oil works extremely well. A massage with SMALL amounts of oil will do wonders. Avocado oil is another superb choice, possibly even better than OO and with less noticeable odour. Other vegetable oils not so much, as they vary too widely from human skin oil composition.