They are terrified of saying something in a response that can cause the church to be seen in a bad light.  Saying 'sorry' might mean the church has made mistakes and that its priests are not perfect representatives of God on earth.  Admitting that  priests have not been endowed with the grace of perfect celibacy at ordination.  This might mean that the edifice is not infallible.  So high level training is required in how to respond to the abused.  It would require Kafkaesque wording to acknowledge the letters.  Simple, human wording is fraught with possible terrible consequences for them.