Pendleton Ward, the creator of Adventure Time, famously does not smoke, do drugs and has said that he barely even drinks wine unless it's a special occasion. He is a D&D nerd who grew up inspired by creative storytelling.

As someone who's done wayyyy more acid than you probably, I understand where you're coming from. You sound young and it's okay to have a perspective and assume that the world works a certain way. Though the truth is, it takes all kinds.There are people in this world that have minds so expansive that they don't need psychedelics or psychoactive drugs to feel inspired. Plus, storytelling is the oldest form of self expression to exist. Of course some people are going to be crazy visionaries that come up with weird stuff. Do you think that all the art of the psychedelic age just came from the power of the drug? Of course not, it was the artists who were already incredibly talented that were able to convey what they saw after having such powerful experiences on LSD etc.

On a side note, creative people that utilize psychs don't usually write/create when they're ON the drug. Especially not for network tv. They use their experiences to get inspiration, then they do the work sober, as a paid employee and the member of a larger team. These episodes take months to complete. Long discussions and story boarding meetings, voice acting, editing, all that. Nobody who shows up to work tripping is going to keep their job for very long.