Why the government prevents legalization of marijuana?

It is absurd that the government will not legalize marijuana when it is not deadly , nor is it harmless and it takes ample amount of dosage to cause any minor altercation of the body, it also has no harmful side effects. I don't understand why they allow cigarettes , aalcoholand ample or other products that are harmfull to everyone. The cigaretss kill , cause cancer , long problems etc , they know alchol causes a variety of diffeent harmful(some cases deadly). There are a large group of children and teenages who smoke cigaretts and drink alchohol and DIP . The majority of tobacco products and alcholic beverages and drinks are easily obtainable. If you were to set up a set up a scientific study provided with; Alchol , cigaretts , and marijuana and see which products can be easily used I would garentee they would get in the alchohol first , the cigaretts second , and would take a while before they were to use the marijuana properly. Marijuana is in fact benifitial to ones health and in many circumstances essential for you health. It does not cause in altercation in ones thought process , in fact it helps. Find any thing pertaining to marijuana that has a dramatic side effect on humans health. And find anything that is beneficial from tobacco products like cigarettes , cigars , DIP , etc. And there are some alcohols that have some beneficial properties