The previously developed geomorphic index of lunar surfaces is applied to the surface distribution of the lunar hot spots. It was found that the hot spot number density is the highest in areas of intermediate geomorphic index, corresponding to mature maria. Young and old maria and the terrae have fewer hot spots per unit area. An hypothesis is presented relating the probability of formation of a hot spot by impact with the evolutionary stage of the regolith of the target surface. The older is the surface, the deeper is the regolith and also the smaller is the average boulder size. For these reasons hot spots will be less probable. The paucity of hot spots in young maria could also be related with the evolution of the regolith, but fundamental changes in the petro-physics of the mare effusions cannot be ruled out.