User blog comment:Belanderanime/Question about the 3 FUTURES, 10 000 dragons PLEASE HELP!!!!/@comment-7418318-20130707183624/@comment-7418318-20130707184657

Because she hadn't done it yet... though it's a bit complicated.

The Future Lucy that we saw didn't close the gate in her own timeline and the current timeline wasn't advanced enough for her to have closed the gate already.

But if F-Rogue hadn't come back in time either Future Lucy or Present Lucy would have made sure not a single Dragon came through the gate.