A large kukri is definitely one of the top 5 zombie apocalypse melee weapons. (I'm also partial to the chinese war sword)
That said, it is not exactly wide-spread or widely known, limiting its use in a game.
That's like the first time I saw the SMG ingame and was wondering why it wasn't suppressed because it clearly looked like an MP5SD.
Turns out it was simply an artist's impression of "a submachinegun".