Most people who use drugs don’t become addicted but may continue to use “addictive” substances without exhibiting dependency.
Many “drug-addicts” have long periods when they are unable to obtained their preferred drug. They will often use other types of drug or do without, only resuming their behaviour when the drug is again available.
Explanations and causes are different things. “Addiction” is only an explanation, but it is treated as if it were a proven cause. It is not.