There are many things that provably have much higher risk of harm than cannabis but have no serious attempts underway to make them illegal. Unhealthy food. Motorcycles. All kinds of dangerous hobbies. And alcohol of course. The list is long.

I don’t think it has much to do with wanting to help or protect anyone, or else you would see more consistency in the things people want to make illegal. It’s more akin to religious people who think they know the “right” way to live and want to impose those values on everyone.

Many people just have an emotional dislike of cannabis for whatever reason—seeing its effect on others makes them uncomfortable, so they want to stop everyone from doing it. Soda and motorcycles don’t make them uncomfortable, so they don’t care about those.

How many societies would have made marijuana illegal had the US not done so first and then forced the rest of the world’s hand?

I’m pretty sure alcohol, cars, and guns do more harm, but good luck making them illegal.