I learned recently the science of why you should use shampoo for your hair (as opposed to a bar soap), it’s not just marketing!! I love learning the why of things, let me share this neat little tidbit:
Shampoo has “sequestering agents”. These bind up minerals (found in hard water) that form soap scum. The soap scum is what a makes a bathtub ring, and this can stick to hair. If you have long hair, it will make it dull and greasy; for others it can form on and irritate the scalp. When on the scalp, this can be mistaken for seborrheic dermatitis (dandruff, and greasy itchy scalp).
From an article by Zoe Draelos, MD in DermatologyTimes February 2022
