Good for using older lenses.
I have a large collection of old Olympus Zuiko lenses from the 1970's - 80's that were sold for their excellent film cameras. These Zuiko lenses produced tack sharp images and I wanted to use them with my new Fuji XT-3. The lenses fit perfectly but they require manual focusing (obviously) and the aperture needs to be stopped down manually as well. But for the price of the adapter I have some excellent prime lenses at my disposal.