Why is marijuana illegal?

Ok. I have been reading many articles about this, and I still have not found a legit reason why its illegal. I can see why they say it would be hard to tax..but on the other hand even though its a natural weed it does not grow strong and potent just in any place. I have tried to grow a plant and it is more complicated than it seams. Light, temp, nutrients in soil, and air all come into play. Who has the time and money to buy the many things to grow it right. Some places it grows ok outside but not many. Control it like ciggs and alcohol: no private plants/home breweing, no selling to minors. Another thing is it would be great to tax because of the way people can make it just like ciggs. For instance, can any grow the plant potent enough to grow those red hairs and crystals that grow easy Companys that make ciggs can make marijuana ciggs by adding diff kinds of flavors, types of plants, diff paper it comes when in cigg form. People would buy it because of the things that come out with it. You can smoke a whole blunt of weed and still not be even close to the disorientation of a beer. Ciggs are man made with chemicals..unless ur dog pisses on ur plant u have diff chemicals that arent naturally made by the plant. Anyone have a comment?