Like I needed this post to tell me that women smell better than men. First of all, they're less hairy, which means .... oh, I misunderstood the title.

Why do women have such an advanced olfactory bulb system? What purposes does it serve?

Not too many years ago, half the world's population were cooks and nutritionists. They were called women, and they were responsible for what their children and their men ate, and whether it led to health and growth or the reverse. So maybe they needed to be able to smell better so as to detect poisons better. Given how our sense of taste owes a lot to our sense of smell (I believe you are familiar with the 'pinch your nose, close your eyes, and have someone give you different foods and see if you can tell what they are' test), it's not too far-fetched to theorize their sense of smell may be superior for this reason.

Maybe. Who knows! It's as good a theory as any.