Well....because...because of the Journey. Not every Chosen is successful, and even if they are...they don't tend to return. [Which Fuuka can probably guess some amount of the truth of what is supposed to happen to Colette back home. With something like that weighing on her shoulders, it did not seem fair to take any relationship too far. Doing so would only end in more pain when they found out the truth, that Colette was supposed to die. And even those who would make it to the Final Seal, they would be taken as potential candidates to be a vassal for Martel and all.]