Because no matter how visually and narratively striking it has been and could be, it is not enough to give female characters like Beverly Katz and Alana Bloom spectacular deaths.
By emphasizing the comedy here, he manages to make palatable the idea that humanity is doomed, our institutions are hollow, and our social structures are meaningless in the grand scheme of things.
Every single film or television show you watch with flesh-eating zombies in it is either inspired by, or responding to, Night of the Living Dead. Every single one.
Statham’s Mechanic, however, is very much an action movie, and moves the focus from being a character study of Bishop to the mentor-student relationship between Bishop and Steve.