Why have we evolved the ability to smell very specific chemicals we would never have been exposed to during our evolution?

As a chemist, I am constantly amazed by the variety of different chemicals that are identifiable by their very distinctive odors. It makes sense why we evolved the ability to smell things that might have been relevant to our survival, like rotting meat, or acetic acid (rotting fruit), fruit esters, smoke, cooking food, etc. But some chemicals have a very distinct smell that doesn't resemble anything that I might expect to find in the wild. For example, xylenes (magic marker smell) are very easy to identify by smell, and are structurally dissimilar to anything I would expect to find in nature in any amounts.

Is this merely an accident of our evolution, or does it imply that the ability to easily identify xylene by smell gave some advantage to our ancestors?