Annie, I assume you meant that most shampoos are not made WITH KOH, not CONTAIN because of course all the caustic is consumed in the reaction with the oil and the finished shampoo wouldn't contain any.
Commercial shampoos are detergent based (soaps and detergents are both surfactants), and these are generally kinder to your hair. But some people still prefer SOAP for their hair - liquid or bar. If it's liquid we still call it SHAMPOO.
Yes, you can make your own shampoo using KOH and oils. It's unlikely you will find a local source of KOH. I order mine from AAA Chemicals, but there are other soap suppliers from whom you can order it as well.