We have had the opposite request from users asking for other functions to include this 'do you want to overwrite' message so it is seen as essential by other users.
We have not set the ability to turn this off so that any questions around why it has not checked that it is acceptable to overwrite occurs.
Well, as long as there is an Undo capability then in my view this pop-up isn't necessary. But if other users want it why not add an option to suppress it?