Doesn't anybody else ever giggle when something is not funny? Like when a situation is uncomfortable, embarrassing, horrifying, or simply overwhelming in such a way that a more articulate response is impossible (and would be inadequate anyway)?
If we were cats, laughter would be our vocabulary of purring but also of squeaks and wails. Those more specific, communicative meows we'd save for requesting food or reporting on mice.
Poor laughter. So misunderstood.