Do you know why they put sodium chloride (halite, ...salt, NaCl) in shampoo? This guy wrote to the company to find out.
Shampoo comes from many manufacturers all over the world. Because a standard formula does not  take into consideration, humidity, because remember glycerin draws moisture to itself. Each batch, from day to rainy or not day, must be uniformly consistent (or we wouldn't buy it three times) so they add an adjustable amount of salt to raise the viscosity to a specific level and that is why we question when our dish detergents are not quite not as thick as they once were?