What happens if you want to switch crew? You have one going to Colonia while you're waiting for them. But you can't use them because they are transferring your ship. There should also a chance they can be destroyed.
Good point, you probably don't want to put your expensive ship in the hands of a rookie NPC you just employed and send him towards Colonia, with the expectation that nothing can go wrong. Maybe not ship destruction, but a high repair bill on arrival and the journey taking twice as long could deter from this practice.
This reminds me of the Fleet missions in NMS, your NPC crew make reports of events that happen along the way. The ships can be lost as well I think, but only if you do not react with reports of major issues coming in.