Efficient use of time.
They can buy time for a business to collect its thoughts, devise a new plan for the future, and implement it smoothly
They can provide stability in a time of turmoil
They can provide greater objectivity that internally promoted staff and, because their term is known to be short at the outset, are able to effect more radical restructurings of individual staff than might otherwise be the case
They will always have operated at a level the interim role, thereby ensuring they are able to impact the situation in question positively and quickly