This is what I thought as well, that the habits that drive some of these activities would be dramatically weakened, but it looks like the body is not actually re-aligning to a new homeostatis level, so when a person gets off the drug, the body is trying to get back to the old level. I don't think it all comes back to habits, often your body is working really hard against you to get back a level it feels is right(whether that level is 'healthy' or not).