CNC machines do specific instructions. They will never assume anything, nor rebel against the program loaded to them. Imagine the security of knowing that you will "reap" exactly what you "sowed". Let's say, something goes wrong during the process. Assuming the machine is in perfect condition, you CANNOT put the blame on it because it just performed what you told it to do so.
Secondly, there is the blanket of consistency. It provides a certain level of safety and ease to the head supervisor. If you have overseen the operations today, most likely, it will be exactly the same tomorrow. The feeling of knowing what to expect is always a good thing, especially when there's money involved.
Lastly, there's speed. CNC machines do not stop to think. After you do the thinking, they do the power-jobs that they need to do. It’s that simple. There is a minimized set-up time and back-job time pocket.
What you will find a flaw about CNC though, is that logic-wise, CNC machines cannot think of better ways to perform a task (IF there is a better way). A CNC machine is purely mechanical; when it was sold to you; the salesmen never mentioned the word “creative” or "innovative". I hope you did not miss that.
CNC machines are also assets of the company. When assets like this are purchased, there is little or no emotional investment that goes with it. You won't even train it! It is expected to do certain tasks and that’s saving you a lot of time from all the explaining, demonstration and reminding.
Also, when a CNC machine is performing its task, it is void of any emotion. So no matter how hot the weather is, or how noisy the workplace is, the CNC machine will do its job just like any other day. It is different as compared to people - who have the tendency to space-out when doing very mechanical and tedious jobs.
Although the CNC may want to, it also cannot complain. That's really convenient. What you will need to note now is your electric bill. Beware, for when getting CNC machines, it may betray you in the form of lofty bills. All the emotions you’ve saved might just be unleashed.