Why set a max file size for registry?

Here is a question that recently came up in one of my courses. I have not been able to find an answer from our instructor or others.
You can set the max file size for the registry in Win2K. Why would you do this? I know the obvious answer, but if you limit the file size and the file is bigger than the limit, Windows tells you, and then resizes it on its own. So why give you the option to set registry size, if you can’t actually control it?