Is there a lore reason why the Warfare factions are always the same?

GTI is always the Attackers and Haavk is always the defenders. Why can't it be the other way around? Especially for the new map, Coliseum, the announcer at the start of the match mentions that Claudia is outside of Haavk's jurisdiction, so wouldn't it make more sense if GTI were the defenders in that case?