Laws create crimes.
We as a society have (chosen) to enact laws against certain activities. It's only because drug use is illegal that it is a crime.
Addiction on the other hand is not a choice. Not every drinker becomes an alcoholic and not every drug user becomes an addict. This would suggest there is something biologically or chemically taking place within the addict's brain that causes them to overdo a thing or crave it to the point of not being able to function without obsessively thinking about it.
We see people who weigh 400lbs and up to 800lbs. Clearly there is a "food addiction", someone who watches porn throughout the day and even doing so on their job, or another who has to go to the casino or racetrack multiple times a week to place bets is getting a "rush" that could cause them to jeopardize their relationships, employment, health, and financial stability has problems.
We still consider lung cancer to be a disease even if a person (chose) to smoke cigarettes for 30 years! We also consider cirrhosis of the liver to be a disease even if that person (chose) to drink a bottle of scotch every night!
The primary reason why we debate whether or not drug addiction is a disease is because drug use is illegal.
We also tend to view "recreational" or "sin" activities differently than we do other things. Some people believe addicts (deserve) to be ill for what they've done to themselves and yet if a person dies from a heart attack due to their high fat and high cholesterol diet with no exercise regime we cut them some slack. It's not illegal to gorge on cheeseburgers/pizza & ice cream.