Folder size for Windows Explorer.

I have really no idea why the size of folder is not shown in Windows Explorer though the size of file is shown under Size column. If I want to know the size of a folder, I have to get mouse pointer paused over the folder and message will be displayed showing the size and other properties OR I juz right-click the folder and click Properties. After I installed FolderSize, I get no hassle - the size of folder is shown. But I needed to do little tweaking – clicked ‘Choose Details…’ under View menu of WE, checked Folder Size and unchecked Size.