Hurricanes clearly abhor the equator and fling themselves away from the warm waters of their birth as quickly as they can. Paging Dr. Freud.
The void circling the image is the equator. Hurricanes can never ever cross it.
Detection has skyrocketed since satellite technology but mostly since we started logging storms in the eastern hemisphere. Also the proportionality of storm severity looks to be getting more consistent year to year with the benefit of more data.