because like marijuana it is not physically addictive or dangerous.
A cat can not overdose on catnip, nobody can, and there are no serious or long lasting side effects.
Human alcohol consumption is a deadly drug compared to catnip, which isn't at any dosage. .It is impossible for a cat to die while enjoying catnip in any quantity.
Edit: Actually David has a good answer. Too bad we have each other blocked. I don't even remember why. It must've been a political thing. He must like Trump. But regardless, I would upvote his answer if I could. Unfortunately, when there is a block, it is not allowed. There was a time, for over ten years while Y!A was green, I never !anyone. Strangely it's only been since Y!A turned blue, but even now I only block those who block me. Seems fair.
Just because catnip is legal, is no reason to smoke it. I'm sure some idiots have, but it didn't kill them.