Using drugs to treat a physical addiction is first and foremost a "coping mechanism" for treating the physical addiction.

When a serious alcoholic is puking themselves nearly to death as they try and get sober, they aren't trying to escape some childhood trauma or "stress". They are trying to escape a physical addiction that has already dramatically altered their mind and body and may possibly kill them.

You may be confusing the cause of drug use with the consequences of repeatedly using addictive drugs. Eventually, the drug addiction replaces all other problems. It's not a representation of other problems.