The mot potent influence on tobacco initiation and maintenance is stress, especially during childhood(1).
Yes, the easy ones with a low nicotine tolerance score (and low exposure to stress) have quit on their own.
Naqvi et al(2) found that the most effective condition for cessation is a stroke in the Insula area. Well, it works.

Misusing exaggerated, guilt-laden, shame based, messages to encourage social denigration and vulnerability, likely increases stress and the risk for cardiovascular disease, and stroke. So, are we creating anti-social, depressed stroke patients who need more care and have an increased risk for Alzheimer’s? Sure, they don't smoke, but can't remember why.

Jay R. Schrand, BSSE
US Navy Veteran
Enid, OK

1. Edwards, VJ, Anda RF, Gu D, Dube, S R, Felitti, VJ. Adverse childhood experiences and smoking persistence in adults with smoking-related symptoms and illness*. Permanente Journal 2007;11:5–7

2. Naqvi NH, Rudrauf D, Damasio H, Bechara A.
Damage to the insula disrupts addiction to cigarette smoking.
Science. 2007 Jan 26;315(5811):531-4.