Why does hard water not form lather with soap?

(N/A) Hard water contains dissolved bicarbonates,chlorides,and sulphates of calcium $(Ca^{2+})$ and magnesium $(Mg^{2+})$ ions. These ions react with soap (sodium stearate,$C_{17}H_{35}COONa$) to form insoluble precipitates of calcium and magnesium stearates.
$2 C_{17}H_{35}COONa_{(aq)} + M^{2+}_{(aq)} \rightarrow (C_{17}H_{35}COO)_2M_{(s)} \downarrow + 2Na^{+}_{(aq)}$
(Where $M = Ca$ or $Mg$)
Because the soap is consumed in forming these insoluble precipitates,it is not available to form lather with water.