When it comes to traditional incense materials--the woods and resins people have burnt for millennia in sacred and healing contexts--their beautiful aromas are clues. Our noses are telling us 'something important is happening--stop and breathe.'
As we inhale those beautiful wisps of smoke, they immediately act on our hearts and minds. They affect us and affect the space itself, changing the qi.
Filling with billows of soft, sweet, resinous smoke, a sick room becomes cleansed and infused with the spirit of health. (Scientifically, we know smoke cleansing removes suspended particles from the air).
If the space was neutral to begin, incense smoke helps makes it positive. And if the space was already clean and beautiful, the presence of true incense raises it still further, to verge on the sacred.
So no, it's not just about the scent. It's about the state. About the space and what's possible within it.