Why is soap not suitable for washing clothes when water is hard?

detergents are the sodium salts of alkyl suphonic acids. They contain a sulphonic acid group istead of a carboxyl group.

soaps are made up of Na and Mg salts of organic fatty acids.

detergents react even with water since they do not form scum, due to solubility of Naq and Mg salts in water.

While soaps donot lather with hard water as they form scum.