Tropical cyclones require specific atmospheric and oceanic conditions to originate, including warm sea surface temperatures (above 26.5°C), the presence of the Coriolis force, and a pre-existing low-pressure disturbance.

1. Role of the ITCZ: The Inter-Tropical Convergence Zone (ITCZ) is a region where the trade winds of the Northern and Southern Hemispheres converge, creating the low-level atmospheric instability and rising moist air necessary for cyclone formation. In the South Atlantic and South Eastern Pacific, the ITCZ stays mostly north of the equator and seldom migrates into these regions, leaving them without the necessary 'trigger' for cyclones.

2. Vertical Wind Shear: These regions are also characterized by strong vertical wind shear (the change in wind speed and direction with height). High shear prevents the vertical development of thunderstorms and prevents them from organizing into a cyclonic structure.

3. Sea Surface Temperatures: While the explanation notes temperatures are generally warm enough, these specific regions are influenced by cold ocean currents (the Benguela Current in the South Atlantic and the Humboldt Current in the South Eastern Pacific), which keep the waters relatively cooler than other tropical basins, further inhibiting cyclone genesis.

Among the given options, the lack of the ITCZ is the primary reason why cyclones do not originate in these areas.