The type of detergent used depends on what it is used for. For shampoo it is important that these molecules are not harmful to humans (like that stinging feeling you get in your eyes) not be harmful to the environment but be good at removing the natural oils and dirt that gets in hair. Shampoo companies put a lot of time and research into trying to develop formulas and recipes for the best cleaning properties along with making them smell good, be safe for hair dye, etc. I am not particularly familiar with glycol distearate. Propylene glycol is a viscous, water soluble dialcohol used in a large number of different applications. In shampoo it is used as a moisturizer.

Hair needs special cleaning because it contains oils that are not soluble in water. Thus, the soaps necessary to clean hair depend on being able to interact with both water and oil, thus being partially polar molecules (like water), and partially not water molecules. Alcohols are simple examples of such soaps, but alcohols are toxic, so are used sparingly. I do not know what commercial soaps consist of.