I know that some drugs are really addicting (like heroin), but alcoholism and tobacco use seem to me to be more like this "sex" addiction. I say this as a person who smoked for 8 years (3 packs/day for most of that time) and walked away without the slightest physical withdrawal. I also drank very, very heavily (sometimes more that a fifth per night) for years and walked away from that with no physical withdrawal.
When I fell in love with my wife, I found a reason to want to live a long life, so I ended some of my stupider habits. I stopped smoking "cold turkey" and reduced my drinking to social drinking (without getting drunk) without feeling the need to drink the way that I used to. For me, it did not even require an effort - just the resolution of mind. I enjoy a few cigars every year without any desire to return to cigarettes. I drink with my friends without getting stupid (never achieve more than the slightest buzz). In other words, I don't have to fear the behaviors because I am in control, not my whims.
I wonder, given my experience, if the people who simply "can't" break these habits really want to...