Part of the fun of games is the shared experience you have with other players, even for single player games. There are certain tasks in games that earn serious nerd cred. When you bake cheating into a game, it further removes the achievement of the time investment/effort because you could have just saved yourself all of the trouble of legitimately accomplishing them and no one would know the difference.
So if you patch out RNG manipulation, you are essentially perfecting the intended game experience.
Now whether FF12's RNG should be altogether preserved in its ridiculous entirety, that's another topic.