If two processes continually trade a resource between them, a third process could be locked out, even though the system is not in deadlock; a system free of lockouts would make sure that every process can get a turn at some point in the future.
If two processes continually trade a resource between them, a third process could be locked out and experience starvation, even though the system is not in deadlock. A system free of lockouts will ensure that every process can get a turn at some point in the future.