Invalid analogy. Tobacco users are productive members of society. Heroin addicts are not. The effects of nicotine are not the same as the effects of heroin. Also, you would be hard pressed to find people who think nicotine withdrawal is as severe as heroin withdrawal.
I’ll concede that heroin is more debilitating, but I won’t concede that tobacco is less addictive. Go to an AA or Narcotics Anonymous meeting and ask how many of them have managed to quit smoking, you might be surprised.
The withdrawal symptoms are different, heroin has more physical withdrawal symptoms certainly, but the urge to want to avoid the withdrawal seems just as strong with both drugs. They both fundamentally become part of the body’s metabolism and the heavily addicted user feels the same need for the drugs as they do for air, water, or food. You might even argue that nicotine is more addictive, since at least with heroin there is some justification for the strong addiction, namely the equally strong narcotic effects. Nicotine, on the other hand, is only a mild stimulant, and doesn’t produce any strong high that would justify the irrational and deadly addiction. So, at the least, it’s more addictive in proportion to it’s effect on the user.