In most parts of the world, marijuana is illegal. Therefore, when kids, even adults, get caught with it in their possession, they get in trouble with the law. Most kids that get a hold of this drug do it because they like to rebel against society, and their parents. And others do it because it helps them relax. .
A lot of people do not understand what is wrong with marijuana to make it illegal. It is considered a hallucinogen, it relaxes your body and mind and decreases your reaction skills. Would you want to ride with someone that can not react properly if something is to happen? It's a very scary thought. It also causes you to be lazy and tired. Most kids in school get bad grades because they go to school too high everyday to concentrate on their work. To be drunk while you are at work or at school is not allowed, therefore if you are high you can also get in trouble or get fired for the same reason.
However, some people just like to use marijuana while they are at home. They don't go out with it and do things to get in trouble. Marijuana relieves stress and helps you relax. Just like alcohol, it alters your state of mind to make you feel differently than you do normally. .
On the other hand, marijuana is known to be a "gateway drug". You start with weed, you get bored with that and you want to be more high, so you start to do other drugs. Those other drugs really can mess up your life, because they can be addicting. It is also very expensive to buy marijuana, and if it was legalized it would be more expensive because the government would tax it. Marijuana also causes "the munchies" which makes you hungry. So if everyone smoked it, everyone would be hungry all the time and eat more than they do now. Would they stop caring about their weight? They could be too high all the time and too hungry to think about it. .
Even if marijuana was legalized, a lot of people disagree with using it. Most thing that if it was legalized it might decrease crime rates.