I understand your thinking but, that doesn't make sense to me or could be very confusing in many scenarios in the game development process, if you really think about it but, you can right click and select "send to bottom of layer" or use the Z order dialog box. Also if you place them on separate layers, (which is a better development practice) you can hide the layer by unchecking the layer in the layer dialog box. This is especially a better practice to avoid confusion during the development process as you'll find out when you start to develop more complex games.
Hope that helps.