Incense is part of Traditional Chinese Medicine (TCM). The aromas affect the body through various channels. It is essentially a gentle form of acupuncture.
The photo shows sandalwood after traditional processing.
I am not a TCM practitioner, so I am not qualified to speak about the deeper and more subtle processes of aromas. The information presented here is for a general understanding of the processes.
Different aromas and their energies enter the body through different channels and activate the movement of certain energies.
In ancient times, specially prepared formulations of incense were used to treat the emperor.
According to TCM, all natural ingredients inherently contain some 'poison' that can be removed through processing, such as heat treatment. Although different ingredients may require different treatments.
The easiest way to visualise this is with a food analogy. We process food and prepare meals - to make them tastier and easier to digest. 
Fermented cabbage is much easier to digest than raw cabbage. The body uses fewer resources to digest fermented foods than raw foods.
Thousands of years ago, Shennong, also known as Wugushen, tasted hundreds of herbs to test their healing properties. He created Shennong's Divine Book of Herbs and Roots, which is the basis of traditional Chinese medicine.
Our ancestors have since discovered that almost all herbs contain some toxicity. It has been said, "Every herb is three parts medicine, seven parts poison". The aromatic substances in spices are often used to fight infections rather than for flavour.
Ancient doctors began to develop techniques for treating herbs to remove their toxicity. These techniques are called Paozhi. Their aim is to increase efficacy and reduce harm.
It's the same with incense. Processing removes the unpleasant notes and replaces them with smoothness and depth. For example, the top notes of sandalwood are often harsh and unpleasant. Processing removes them.
Processing also prepares and reveals the chi of the materials. Processed incense goes deeper into the body than raw incense.
I usually give an example like this. Raw materials - looking at the cats in the zoo through the glass.
Processed incense - stroking a cat on your lap and feeling it rumble.
The difference is incredible. I spent half a year learning this technique. And once I had learned it - my whole understanding of incense turned upside down! A new wonderful world opened up)
Processed Agarwood sticks. They are a fabulous cosmos, I am really proud of them.
Why do only a few people do the processing? It's a complex process that requires knowledge and skill. You can't do it on a large scale. I prefer quality over quantity.
All my incense is made using traditional methods. I especially recommend trying Sandal, Nameless Orchid and Agarwood. The processing is most evident in these. And the aroma and energy can deeply affect the body and mind.
You can read more about them and choose from them on the website
https://momentomaterial.com/