"Potential for abuse", not "addiction" is the legal standard the DEA uses to classify drugs. And actual harm to society is factored in. Caffeine is more addictive than steroids, yet guess which one is a DEA controlled substance.

Nobody denies that heroin is extremely addictive. Total harm and "potential for abuse" caused by alcohol and tobacco would likely land it somewhere on schedule 2 or 3 if they weren't economically useful for their profits, despite their "potential for abuse".