Most people simply don't earn enough to become wealthy without compounding. Many do without low-value items to save for things of higher value. They know that small savings here and there add up. People who learn skills that are in demand by employers are in an especially advantageous position. Workers today should never consider their education finished.
People also tend to meet their mates at college, which further increases their earning potential.
Thus, they tend to earn more and have more wealth than singles. Marriage is not essential for wealth accumulation, but it helps. Married couples often enjoy economies of scale. In addition, marriage has been shown to be associated with better health than single persons. Divorce, on the other hand, can deplete financial assets due to fees for lawyers and maintaining two households instead of one.