Why does this SUPER simple line of code take 35% or my processing power?

For my Job I am trying to create a Heartbeat program that monitors the status of interactives. In order to do this safely, I don't want clients closing out of the program, so I want to hide the window.

This is the single line of code that causes 35% of my processing power to be used when I run it. There is nothing in the scene and no other scripts.:

 void OnApplicationFocus(bool hasFocus)
 {
    User32.ShowWindow(User32.GetActiveWindow(), 0);
 }

Once you build your application, this code should immediately hide it. Now if you open Task Manager, you can see that when the application is hidden, it takes a lot of processing power. Anyone know why?