It's just policy and this perpetual war on a substance that's led us to where we are today.
From a toxicological perspective, alcohol and marijuana are so different, it's not even funny. From the angle of addiction, sure, you can abuse weed, but you can also abuse sex, eating, working out, other substances, etc, etc. But you will not kill yourself from an overdose on marijuana.
It's been a prolonged attempt at another prohibition. And as a result, it's created a dangerous black market, bolstered mass incarceration, and led people to believe things that are patently false.
Our grandchildren will look back at this in the history books and laugh. Tax it, create policy that keeps young children from getting it, administer well designed tests to confirm if someone is on it at the moment for law enforcement or the work place, and call it a day.