Because to resolve them a revolutionary situation is necessary first, and then some class leadership ready to lead it towards victory. Instead the impasse or temporary fixes for social peace will just continue into years of unresolved tensions erupting every once in a while but not achieving much. I.e. when

(1) when it is impossible for the ruling classes to maintain their rule without any change; when there is a crisis, in one form or another, among the “upper classes,” a crisis in the policy of the ruling class, leading to a fissure through which the discontent and indignation of the oppressed classes burst forth. For a revolution to take place, it is usually insufficient for “the lower classes not to want” to live in the old way; it is also necessary that “the upper classes should be unable” to live in the old way; (2) when the suffering and want of the oppressed classes have grown more acute than usual; (3) when, as a consequence of the above causes, there is a considerable increase in the activity of the masses, who uncomplainingly allow themselves to be robbed in “peace time,” but, in turbulent times, are drawn both by all the circumstances of the crisis and by the “upper classes” themselves into independent historical action.