That's true, however, often one wants to slightly adjust a wonky peace-settlement, or split conquered territory with an ally, à la the partitions of Poland (slightly before the game's time-frame, I know, but you get what I mean).
It also gives laymen a limited modding capability, say if they want to play a scenario in which country X had never lost province Y or whatever, and can't/don't want to mess with the text files and code it in themselves.
You can't just assume people are going to use it to cheat - and even if they are, it's not your place to condemn them for it. More power to the player is always a good thing, replayability-value-wise.