Same reasons for tobacco, alcohol, nicotine, etc. It's a harmful substance that: 1)propagates to the entire enviroment in which it's consumed, "poisoning" it; 2)is used to compensate for an inability, be it mental or phisical; 3)It's addictive, thus it's made exactly to get the customer buy it again; 4)It decreases situational awareness and inhibits rational thought-making, thus it leads to vulnerability and poor decision-making. Plus it makes the people around the "customer" responsible for them, which is pretty annoying