The safety net of a failed joke is that it doesn't mean very much. Putting authoritative rules in place to prevent a failed joke makes it so much worse when a joke doesn't land, or accidently offends, because now it "shouldn't have been allowed in the first place" and the public senses a disruption in their own control over the world.
Just let jokes go people, they don't matter and that's the gorgeous, beautiful truth we can share together. The network effects of treating jokes like they have authority and governmental consequence is deeply unpleasant for everyone, except a few political groups which benefit.