First, photographers that are obsessed with night views. If you want to take a well exposed photo in low light, you need a lens with a wide enough aperture to let in more light. Using this lens that goes down to f/0.95, for example, is a great way to let enough light in and make the frame bright.
Second, for portrait photography. The 33mm short focal length with a fast f/0.95 aperture allows you to capture stunning images with a shallow depth-of-field, letting your subjects stand out from their backgrounds. Moreover, it allow you to collect more light towards the sensor and therefore reduce the exposure time to better freeze movements or reduce the ISO sensitivity to obtain a better image quality.