Remember Film Rolls?
If you don’t know what film rolls are, just imagine that they’re ammo for your camera. Back in the day, you could only take so many pictures on a single roll of film before needing to swap it out. The camera would make a whirring sound when it was out of film, letting you know when to replace it.
This husband probably had no idea how cameras worked. He just kept taking picture after picture, even after the 36 shots of their roll ran out. After asking the OP, who worked at a camera shop, the husband learned that he hadn’t actually put anything in the camera. Every picture they thought they took was nothing but a memory.