The literature on this is clear cut. People absorb, metabolize and experience drugs differently, which has a big impact on how addiction takes hold. It's obviously not the only factor! But it's a big one and somewhat quantifiable.

Personally, I wasn't a "trigger" smoker, I was an "every chance I got smoker". I assume my nicotine metabolism is higher than average, which is linked to frequency of consumption and hence propensity for addiction. I also assume I have fast caffeine metabolism since I consume it at all hours with no consequence, but unlike nicotine that's linked to a lower propensity for addiction, which matches my experience.