Chain smoker

My mom is a chain smoker. She quit cold turkey back in the early 90's and was doing really good until she fell off the wagon 3 years later. It's been non-stop since. I don't understand the addiction. Could it be hereditary? I remember my grandmother being the same way too. Her favorite was swisher sweets cigars. Nah, it can't be. I tried smoking too, but didn't get hooked. I don't like the smell it leaves my hair and clothes. Last Christmas, I thought about buying electric cigarette for my mom. I wonder if it really helps???