My theory of income smoothing states that your total income is much more than monetary income, and can also include time and opportunity.

Currently you have time and the opportunity to hang out with a fantastic girl, though the money lags. Soon, you will certainly have more money, but probably not as much time nor the chance to hang out with a girlfriend (either she'll be your wife and you'll be prohibited from seeing other girlfriends, or you'll be on to the next g-friend).

Some say this leads to irresponsible spending by youngsters, but those who use their assets most effectively tend to get more out of life, and assets include more than money.