Just like we say a Bracha before eating we also say one before enjoying pleasant smells (not only at havdala). Even though it is only an enjoyment, and not satisfying a biological need, it still calls upon us to praise God as the creator of the world that we are enjoying.
Just like the blessing before eating, this obligation forces us to categorize nature. When we smell a flower we will need to ask if it is a perennial (Borei Atzei Besamim) or an annual (Boreh isbei Besamim). Due to our botanical ignorance we typically say “Borei Minei Besamim”, which is generically applicable to all smells, but ideally we should notice, and praise God, for the particular source of our enjoyment.