Smell is important to many species when it comes to competition as you mention in your post. Scent is also important when it comes to mating.

Smell is important to many species when it comes to competition as you mention in your post. Scent is also important when it comes to mating. Some female species emit odors that indicate whether they are a virgin and if not, how many times they have mated. If you were a male, what would be the advantage of having this information?