The tech doesn't require a screen refresh, if you don't refresh the screen it leaves behind "ghost" letters. They flash the entire screen because if you just wr

The tech doesn't require a screen refresh, if you don't refresh the screen it leaves behind "ghost" letters. They flash the entire screen because if you just wrote all white to a screen that had letters, you would still be able to see a difference between pixels that were previously white and pixels that were previously black. You would have to choose between an entire screen refresh on backspace or leaving it slightly messy looking.