Does documentary photography have to shoot people?

Not exactly. The so-called documentary theme refers to a reality, which can be a social phenomenon, a person, a rare thing and an object. For example, if you shoot a handmade product in a handicraft workshop, no one will participate. Who can say it's not a documentary? Documentary actually covers a wide range, which may be a person, an event, a scene and a reality, but it will not be retouched like a special portrait or scenery film.