Silly question: Why does Layout let you set a circle by diameter... namely typing for exampe: 5" d in the toolbar to get a 5" diameter circle and Sketchup itself does not?

I was dealing with this today. The Mac version can have a totally custom toolbar by simply choosing View -> Customize Toolbar (the last entry on the drop down). MY question, however, is why in the world did Sketchup take AWAY the ability to customize the toolbars in the Windows version??? I started on SKP 4 and have used it all the way to 6 Pro and it USED to be easy to build a custom toolbar... Why take away a good thing? Especially when the Mac interface has such an easy way to do it?