Merriam-Webster does of course have addiction as a habit, but it singles it out as being different than other definitions https://www.merriam-webster.com/dictionary/habit

perhaps this is one of those definitions that are in flux and we are moving from taking drugs as a habit, to first having a drug habit, and soon, no longer a habit but an addiction.

I would have to say that in light of the other definitions of habit it does seem reasonable to separate them.