Q&A: Why do people use apple cider vinegar rinse after washing with alkaline products? Why not just make the shampoo bars with very low pH? (Tons of information about hair chemistry and shampoo bars…)

In the July Q&A post, I live in an area with very hard water, and I’ve heard that could cause a problem when using shampoo bars. I’ve also heard about apple cider vinegar rinse, which does not sound too pleasant to me. Would you shine more light on this? Does the vinegar rinse work because of…