Much of the safety system is dependent on human intervention. Why would you turn on a coffee pot if there was no water in the pot? If you wanted coffee you'd first make sure that you have the machine setup for what you want before turning it on (or possibly using a timer to make sure it goes on after you've set it up). That little bit of setup can be very hard, expensive and difficult to do correctly.
Even something as simple as filling the pot with the correct amount of water requires smaller steps. Oh and if you are explaining this to your spouse may I recommend that you don't use the toilet float to explain how the pot fills with water. The analogy doesn't work well. ;-)