People like to personify addiction, as if there is some outside force controlling the person, but this is to discount and discard every single addict who decided to clean themselves up. I know lots of addicts who chose to continue, and I know lots of addicts who chose to stop.
Don't personify the addiction: the brain of an addict is still that person's brain, and their decisions are still their own, even if they are de-legitimized in your own opinion due to their addiction. There is literally no one else who could possibly be responsible for the decisions of that human's brain and actions than that human being.
What goes in to our own bodies when we are not coerced by another person is our own decision, full stop.