First, because hatchbacks are generally hatchbacks, the rear glass and the rear door are integrated, and the wiper shaft is mounted on the metal door body under the rear door glass. When the rear door is lifted, it will not affect the wipers.
The sedan has an extra trunk to cover the hatchback’s rear, and there is no place to install wipers. It is conceivable that if the wiper shaft is installed on the back box cover when the box cover is opened, the glass does not move. The relative position of the wiper and the glass will be misaligned, so it is not suitable for installation.
Secondly, this is a question about fluid mechanics, as shown in the figure below:
When the car is driving, the car’s space is crowded out by the corresponding size. The air is moving, and the air cannot quickly fill the space evacuated by the car due to the viscous nature of the fluid after the air is expelled.
So a vacuum is created at the car’s rear, creating a vortex. Due to the influence of the eddy current, the rear windshield of the hatchback is more likely to form a more significant negative pressure than the rear windshield of the sedan. It is also easier to roll up dust to pollute the rear windshield and affect the rear view function. The sewage generated by the rotation of the rear wheels of the sedan is almost blocked by the entire trunk, which will not cause the sewage to roll up the rear glass window.
Therefore, the rear windshield of hatchbacks is generally equipped with wipers. When it is raining, or the rear window is polluted, the wipers can be turned on to obtain a clear rear view. But it is not absolute. The rear hatchback sedan is also equipped with rear wipers, but it is not shared.