From a letter written by the National Park Service:

"Right to carry" laws do not protect visitors from wildlife. Most weapons carried for protection from wildlife are not adequate for that purpose. Untrained individuals attempting to protect themselves from dangerous animals often exacerbate the situation.

So I guess when a mountain lion is chewing on your head they want you to use just your bare hands or improvise weapons on the spot like sticks and stones. And I presume struggling and screaming won't exacerbate the situation either. Maybe those National Park bureaucrats are of the type that think just because a proposed solution is "all natural" it's better.