The primary reason is to create a pure, clean, quality oil that is safe to produce with little-to- no post-processing, unlike toxic solvents that may require many hours to purge the solvent trapped in the oil. In addition, multiple industries have proven that the highest efficiencies in commercial processing utilize CO2.
CO2 is efficient, inexpensive and is a "tunable" solvent. The ability to "tune" the extraction process can not be overstated - especially with a system that will separate constituents during an extraction. You can target specific compounds, like terpenes (terpenoids) through different parameters. CO2 is also a sanitizing agent, prolonging shelf life and with the proper system and environment, yields food and medical grade oils.
Supercritical CO2 Fluid Extraction Equipment Price / CO2 Extraction Machine Supercritical is the cleanest, safest method for extracting plants such as hops, hemp and a wide range of nutraceuticals and organic crops.