There's some merit to it, depending on the type of game. In particular using the guide below I turned off enemies' ability to notice the player in Bioshock using a script, which was a pretty cool experience of just walking around Rapture and fucking around with the AI by spawning loads of splicers and seeing them use the environment (you'd be surprised at all the different actions splicers can take but usually don't).
http://gametweaking.blogspot.com/2007/09/
Though on the other hand, a game like SimCity would be a lot funner if crime was an actual gameplay element rather than a result of bad planning (putting residential next to industrial). It'd give the ability to dictate police and firemen actual relevance rather than being a thing nobody touches after disasters. There's nothing wrong with a pure sandbox mode though.