I am not sure I agree with the portrait you are depicting, as if some homeless are there because of their nicotine addiction alone. I would put money on the odds that the homeless you describe feeding their nicotine habits were not out on the street from this habit and it is just one of many addictions they have. It is just the easiest to feed because of how many ashtrays and smokers in the world there are they can feed off of.
But I don't think for a second, once they find a cigarette, they aren't moving on to the next need…alcohol, heroin, meth, etc.
Im willing to bet over 90% of hard drug and alcohol addicts are also smokers. But it wasn't the cigarettes that got them on the streets.
So i am sorry, but i don't really agree with the description you provided as an apple to apple comparison of the addiction issue. To me, drugs should be continued to be dissected and segregated in classes with their own restrictions/limitations based on the various levels/degrees they have an effect on the body and mind. We shouldn't group them up.
I do agree Portland has a huge disconnect in many facets of their ongoing and growing issues. Portland is very much reactionary instead of proactive.