Concentration and Insight

Should one not develop calm first, so that insight can be develop afterwards with more ease?

One says that calm is helpful, but why does not say : all moments of kusala (wholesome) are helpful? Why does one not develop more kusala in daily life instead of high levels of calm. Any kind of kusala through body, speech and mind brings calm, and at such moments one does not think of oneself or one' problems. Each kusala citta is accompanied by calm.