Marijuana is not legal because it causes a "high". The pharmaceutical companies will not allow the drug to be made legal, they will withhold fundraising campaign dollars if any party were to start a bill to legalize it because they would lose too much money - marijuana can make a person's medicine cabinet lose more than half of the pill bottles. It alleviates the symptoms of hundreds of diseases and ailments, from pain to cancer, radiation and chemotherapy side effects, ALS, MD, you name it, pot has some beneficial use!
But, for recreational use? It will never be legalized because the government would not be able to control who sells it, just like it is now