When you find a single error you can ask for a retransmission and expect to get it right the second time, and if not then on the third time, etc. However, if the message in storage is wrong, then you will call for retransmissions until another error occurs, and you will probably have two errors which will pass undetected in this scheme of single error detection. Hence the use of repeated retransmission should depend on the expected nature of the error.
