Because by deleting it we allow the write address message to be retried, which is the correct behaviour (we do it with the WRITE_FLASH messages, so we should do it with the WRITE_address).
I could check that in a case where the acks from the motor were lost (due to a FW bug in the palm) removing this return allowed the FW to be programmed successfully on the motor boards. Although error messages are printed when a packet has to be resent.