737 Jockey.. I'd guess timing. Being in a hold pool works both ways. The majority of us have a life outside of work, and real world things come up. Things like weddings, birth of a child, holidays, bereavements are some obvious reasons as to why someone might delay being plucked out the pool. The list goes on, but it's unlikely those applying as a DEC are looking at the phone the whole time they're swimming only to answer it and decline a job for no reason.