The disease label started with the legalization lobby.
It’s part of that movement. First decriminalize, then move to legalize. It’s worked with pot.
The disease label started with treatment for alcoholism. The terminology was soon expanded to other addictive drugs. A traditional difference, now eroding, between alcohol and rest is that alcohol has generally been regarded as socially acceptable (with a nod to very large abstaining communities) and legal (except during Prohibition). It is not only socially acceptable but is widely celebrated and encouraged.
But the casualty rate is pretty high, and always has been. Alcohol is almost universally addictive, for example, among American Indians, Australian aborigines, and other native people who were not exposed to it prior to European contact. It also clearly runs in families, and among human populations that have historically used alcohol, the incidence of addiction varies by race.
It is easy, when alcohol is a traditional and accepted drug, for those who can use it safely to look down their noses at people who can't. "I can do it; you must be a moral defective if you can't." Those attracted to this line of argument should take it to an Indian reservation and try it out there. Obviously, individual susceptibility to addiction varies widely. Obviously the dosage is important. And obviously, cultural and psychological factors come into play. That makes it complicated. But it is clear that the genetic component is real.
Among the other addictive drugs, individual susceptibility also varies widely. It's best to stay away from them altogether, but medical addiction provides plenty of examples of people who are taken despite being on a moral high horse about how they are too moral to get hooked. It doesn't work that way.
The addict does have a moral obligation to stop using. But that is very hard in the face of a serious physical addiction.