Why is Marijuana (weed) so commonly used even though it's illegal?

I would say its because they find it more attractive than other things,some people dont drink but they smoke, and some even say its because its a herb therefore not really harmfull(wich i dont think so). Studies have proved cigarrets wich contain more than 4000 chemicals in it, are much more harmful that Marijuana(weed), its also been proved that no matter how much you smoke you would never had a overdose from marijuana,you could easly reach an overdose with simple paracetamol pills.So my theory is that Marijuana is illegal, because its easy to grow, its highly profitable to sale, also very easy to get consumers,and for the goverment it would`nt be very good,to have such a profitable product on the market. In my point of view that is the reason why its a illegal drug.Because the goverment wouldt benefit from it being legal.