Because it's more than that. It's also a study of loneliness (of both main characters) and obsession. It does have its shock moments, not least when in becomes clear that Maud is not the clear-cut character you thought she was.
As I left the cinema, I quoted Dave Allen to myself: "I'm an atheist, thank God."
As I left the cinema, I quoted Dave Allen to myself: "I'm an atheist, thank God."