Often in my typing, I have need to leap for the "backspace" key. It happened twice typing the last sentence. When I do, once in a while, I'll hit the "insert" key on my keyboard. All of the sudden, I'm typing over something I'd already written, and once I realise that I have to undo it or retype it.
This feature may have had a function in, oh, the '80s, but since the advent of the mouse it is much easier to drag over the part you want to delete rather than type over it. I mean, this function has been obsolete for twenty years, an eternity in computing terms, yet not only does Windows still support it, but the keyboards are designed to put the insert key half an inch from a big key that is often used (and generally flailed at).