Pick one:
-Because the AI always builds the orbital fleet manager. On every planet.
-Because you aren't playing TA 2.02 with the orbital command center, which is a super project that replaces the orbital fleet manager, since it replaces the need for it-the effect of the SP is the same as having an OFM on all of your planets.
-Because you are playing TA 2.02 and the AI has built said SP.
(It's unlocked via Interstellar Construction, after Artificial Gravity.)