4. Makes repeated task tedious and boring. If you want to change all file names from something like xxx_1234.jpg, to yyy_1234.jpg and yyy_1234.jpg, what would you do? Change them one by one in the GUI, yuck. It is boring to do it with 10 such files, a full time job doing it for 10,000 and virtually impossible to do it with 1,000,000 files.