If you have a Battlecraft guildleve in your possession and you initiate it at the aetheryte and then abandon it, it becomes marked as "failed" in your Journal. When you speak to the NPC at the guildleve counter after the next cycle reset, that guildleve automatically changes from "failed" back to "unused" so you can once again initiate it as normal at the aetheryte.

Why do players do this right now? There are only a handful of really good guildleves to get SP from at the high ranks, so parties will intentionally fail them in order to keep them for next cycle rather than completing them and being forced into waiting for them to pop up again at the guildleve counter. This also allows you to do the same guildleve twice in a single cycle if it pops up again at the counter and you already have it in your possession. All you have to do is use the one you have on you and then go back to the counter and grab the "double" and you can use that one too.

Leve link parties are the only good way to level at the high ranks, players make the most out of a flawed system.