This is very much a nature over nurture take. Many people lack the willpower to avoid succumbing to constant barrage of all the modern world's immorality. The ancient Religions knew this and sought for the betterment of society to specify morals to abide by. As such under a more moral society for generations, even individuals who could only avoid temptation by not being exposed to it, were productive members of society. The masses of the middle part of the distribution are more a function of nurture than nature and as such the sheep require a good shepherd to keep them from being led astray.