Considering the sheer size of it, they'd probably have to send a rather sizable fleet to tow it all the way back to a castrum capable of servicing it. Especially if it can't stay in the air at all on its own. And that entire fleet would have to pass over hostile territory, not to mention the various horrors in Azys Lla itself. The logistics are a nightmare. So they just strand a small force of conscripts up there to keep the savages out and otherwise ignore it.