Ever wonder why someone who uses tobacco products are treated with essentially the same drug they are getting from tobacco?
The other components of burning tobacco cause all the harm. Nicotine is the addictive substance which is why we use it for treatment; however, nicotine itself is not causing cancer, heart conditions, or strokes. Without Nicotine, people would not use cigarettes or smokeless tobacco. In order to wean the brain off of the substance with (hopefully) little withdrawal symptoms, we substitute with nicotine replacements (patch, gum, lozenge, nasal spray, and inhaler).
Going back to the addictiveness of Nicotine, when inhaled through a cigarette, it is the fastest delivery of the drug to the brain; 7 to 10 seconds to be exact. Once the Nicotine has reached the brain, it releases an explosion of dopamine (feel good natural chemical), which is why the addiction can be so powerful. When we look at the delivery of Nicotine replacements it is much slower (several minutes) making it rare that individuals abuse or become addicted to these products. The products help to fill the void of nicotine from a cigarette and with the slow and steady release it allows your brain to crave less and less over time.
Here is a graph that demonstrates this: