Aromatherapy depends on the ability to buy organic and essential oils, which are the essence of certain plants. They are not available in the mass market because lowing oil is a fairly large task, it involves not only taking oil out of the factory, but the process to turn it into oil which is actually a complicated procedure, and a different process is used depending on the plant extracted. You can find out the pure essential oils via https://chakralands.com/essential-oils/essential-oils/.
Image Source: Google
Here there is a good explanation of what is actually essential oil, and how the results are.
The ancient way involved it applied a piece of glass at the bottom of the wooden crates with pork fat, and leaving fresh flowers basically chaping pork fat for several days, while adding new flowers to batches continuously until the fats fully absorb plant oil. Then, oil, called "pomade", was dissolved by alcohol. Alcohol separates plant oil from fat, and then dissolves completely, leaving only the essence of plants – pure aromatic oil from the original flower.
While historically people generally use pig fat from various animals, today is common to use what is basically vegetable fat, such as palm oil. Cane is also used, and this is the cleanest oil for use. So, while oil can be made from ancient methods, there are contemporary changes, or adjustments, according to time.