Because you can't open social media without seeing music artists, actors, comedians, strength athletes, social-media-only-famous people shilling for one company or another with sponsored posts.
>it is very effective for many people.
Placebo is a hell of a drug. There is no credible, replicable, evidence that CBD does anything for anyone, and it's done nothing for many people duped into buying it, it's likely acting as a placebo. It's all n=1 posts, "my friend's uncle has cancer and took some and man it changed his life", SEO advertorial blogs and 'press releases', forum posts etc.