I will say that my husband smoked a lot, drank and did meth. He cut the meth first. Now, he rarely drinks (just wine on occasion) and has just now put away the cigarettes. I think the cigarettes are challenging because they become ingrained in your habits: i.e. after dinner, after sex, first thing in the morning, etc. He admitted that after a meal, he would get a rush of "anticipation" in looking forward to his next smoke.
I think someone mentioned the idea of finding it hard to focus on both the drug addiction and the smoking addiction. That makes sense to me. My husband's words were something like, "I'll quit the smoking, but let me get some time under my belt with the drug addiction first."