Early TVs varied in their displayable area due to manufacturing tolerance problems as well as a process called blooming, where the image size increased slightly when a brighter overall picture was displayed. Because of this, TV producers could not be certain where the visible edges of the image would be.
I actually had a double quote on my clipboard I'm a programmer and find Ctrl-V easier to "type" than actually typing a quote when I need to put a bunch of lines of text in quotes.