Phaneron

Answer: For one thing the engine running the pump isn't that loud. The characters have conversations at a normal volume without having to scream at each other. Even if the conductors could hear it, there is no reason they should care or be suspicious. It just sounds like an engine running in the distance and they don't care enough to look for what is making the noise. At that very moment there is also a kid riding a dirt bike in the area. Engine noises are a very common thing.

BaconIsMyBFF

Answer: As the other answer indicated, it is a common filming technique used to achieve various visual effects. Handheld cameras can create a deliberate sense of movement that follows a movie's action. A cameraperson can physically move in much closer to an actor, creating a more intimate connection between the character and the audience. It can also reflect a character's movement from their vantage point, and can be used to create a greater sense of realism with an edgier, less-rehearsed, or a documentary-style feel.

raywest ★

Answer: It is a style of filming a scene, a style of camerawork. In your opinion it doesn't add anything, but they do it for that purpose.

lionhead