Much to the utter disappointment of Sims fans, promotions do NOT always result in more money, more happiness, and more WOO-HOO. Promotions in the real world however, do.
Every promotion has it's advantages. Depending on your current position, a promotion does most of the time entail a significantly higher standard of living and for some the aforementioned WOO-HOO . There are ways to increase your chances of a promotion. Among those is to slave away in your depressing little cubicle, constantly thinking of ways to improve the company and all the while doing a metric fucktonne of paperwork. The second way of course, is to practically (and sometimes literally) cup the boss' balls in your hands to keep them warm and toasty and generally put his happiness above everything else. The latter is more likely to make you a subject of hate and dick jokes among your co-workers, while the first is more likely cause depression and a few extra nights on the "happy pipe" but hey, nobody ever said promotions came easy.