Because people have passed laws against some drugs and not against others.
I'm going to take a wild stab here and guess that the person who asked this question was a teenager, because as you get older you tend to get more cynical and stop expecting that the law, or rules in general, will actually make any logical sense, at which point you recognize that the answer to questions of this nature is "because that's how things are."
It's certainly possible to argue that Substance X (let's pick, oh, say, marijuana) should be legal. It's equally possible to argue that Substance Y (let's make this one tobacco) should be illegal. And if you feel strongly about that sort of thing, then you should definitely campaign for it.
What you should not do is assume that the people who wrote the laws, in many cases several decades ago, had the same notion of how things ought to be that you do.
cigarettes
Marijuana is harder on your lungs, but given time, you can get lung cancer from both. Cigarettes are legal, Marijuana is usually not. From a health perspective Cigarettes have more known and proven health concerns than Marijuana.
cigarettes
Cigarettes can, but no marijuana does'nt.
Purchase Cigarettes, apply for medical marijuana, attend strip club
Cigarettes.
There is no nicotine in Marijuana, nicotine is in cigarettes.
Cigarettes kill millions of people a year. Marijuana has killed 0 people in over 10,000 years.
because tobacco is not easy to grow. therefor it is easy for the government to monitor and tax all of the cigarettes or any other form of tobacco. However marijuana is very easy to be grown and harvested, and can be done indoor or outdoor. if it was legal, it would be nearly impossible for the government to tax you for it, and they wouldn't make any money if marijuana was legal.
weed gets you stoned cigarettes dont get you high cigarettes suck! also if you smoke marijuana with a bong or a vapo its much healther; (most people for get that when compairing the two.)
no they dont exist.
Marijuana is always better than alcohol and cigarette smoking.