It improves low-light performance while still allowing for highly detailed photographs in good light.
Normally, an increase in megapixel count on a constant image sensor size would lead to a sacrifice of the surface size of the individual pixels, which would result in each pixel being able to catch less light in the same time, thus leading to a darker and/or noisier image in low light (given the same exposure time).
[4] Some systems use more advanced algorithms such as considering the values of nearby pixels, edge detection, self-claimed "AI" etc to increase the perceived visual quality of the final downsized image.
This aggregation, although associated with loss of information, reduces the amount of data to be processed, facilitating analysis.
The binned image has lower resolution, but the relative noise level in each pixel is generally reduced.