The answer is that many people do use such treatments. The problem with many herbal medications today involve contamination with pesticides and the impossility of insuring consistent doseage. I was involved for a while with a farm where we produced artimesia, a traditional herb used to treat malaria for thousands of years. Through chemical analysis we determined some plants produced insignificant amounts of the useable medication while others had larger amounts. We selected those with higher yields and bred plants that were far more effective. The techniques to inexpensively quantitatively determine the amount of medicinal substance are relatively new on the scene. On the other hand we examined herbal products from China and found many to be highly contaminated with carcinogenic solvents and pesticides. As to "side-effects" this is a straw dog. Modern medications save lives. It is a question of weighing risks against benefits and that must be done on a case-by-case basis with every medication. It is irrational to condemn "western medication" because of "side effects". In years past the investigation of utility was done on an anecdotal basis, and not double-blind studies. Much of the data on "traditional" medications, unfortunately, do not meet the modern standard of a "double-blind" study.
"There are some eastern medications are with thousands of years proven usable track records."
But not all work as claimed. Many have unproven track records, some proven. Everyone is different, may work with one and not the other. It's your choice which road you wish to take. If genetics does not come into play prevention is the key. Currently there is no proven cure for diabetes.