Basically it's an abstraction. It's easy to say "take off the limit and just make a system that simulates X, Y, and Z instead", but it's really not as easy to make a system like that as it is to write a quick sentence detailing it 
It can also over-complicate the game, means less time for other features, and is another thing the AI needs to think about. At a certain point you just have to set some rules and accept it's a game rather than a full on simulation.
It can also over-complicate the game, means less time for other features, and is another thing the AI needs to think about. At a certain point you just have to set some rules and accept it's a game rather than a full on simulation.