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The most common use case for large apertures on a wide angle lens is in low light, especially wide angle views of the night sky. Because of the Earth's rotation and the apparent motion of the sky, shutter speeds need to be limited to about 600 seconds/(focal length in millimeters x crop factor). Since depth of field is not an issue with celestial objects that are at infinity focus, wider apertures allow lower ISO settings than would be the case with typical apertures used for landscape scenes. Higher ISO settings and the resultant lower exposure values tend to generate noise that is just as bright as many dimmer stars, and thus any applied noise reduction can also "eat" stars.