Wide area economic load dispatch sytem

Hello,

I'm reading one article about coordinate boiler-turbine control, which I'm trying to understand well. I have came across the following:
"Development of the coordinated control system received added impetus when electric power generating companies introduced the wide area economic load dispatch system. This system requires precise load control. Each controlled unit must produce a specific level of megawatts and the area load control system adjusts the turbine control valves until this level is reached."

and also this:
"Wide area economic load dispatch systems require controlling the boiler and turbine-generator together in a coordinated system."

I admit I'm not really sure what this is. Is not precise control of load something that is always desirable no matter to economic dispatch?

Do you have more information?

Thanks in advance...