Why are computer models not forecasts? Why would it be a terrible state of affairs not to have human forecasters?

More specifically, what role do humans play in digesting the output of the computer model and producing the forecast? What adjustments or corrections are made to what the model says is going to happen, and based on what reasoning? "My gut tells me the tornado is going to move east, even though the computer says it will move west with an estimated 98% likelihood"?

Are the humans doing more than creating a human-consumable verbal summary of what the computer model says will happen -- explaining the severity and location of the predicted weather in human terms?