There are tons of issues with cannabis. It severely diminishes your ability to solve problems or concentrate on complex tasks over a period of time. I'm not in favor of people casually being drunk every day, and therefore I am not in favor of people casually smoking weed every day.

If we want people to be able to get the medical benefits of cannabinoids, like anti-emetics, pain relief, appetite, anti-psychotics et.c. we need to research their mechanism of action and synergy between each other. People who are sick do not necessarily also want to be high, especially if you have to take your medication over an extended period of time.