And you'd be right.
Cocaine is addictive to everyone, just as narcotics are. Cocaine is a powerful analgesic (-aine, benzocaine, procaine) and also acts on the brain.
The genetic component is that for folks, like me, a Bud Lite does the same thing to my brain that a weak shot of heroin would do. In fact, they talk about using the same drug, Naltrexone, to block the euphoric effects of heroin AND alcohol.
About 12% of the folks get a bigger "high" from cocaine than others, but it's addictive for all.
And, the rats in one of the first studies kept stepping on the pedal until they couldn't step any more. So do humans.
Arf