OTHER REASONS FOR USING LAYERS
One of the greatest benefits of layers for me is the ability to make changes to any part of a project without affecting the others.
You can use the circle resize gadget to change same size circles as a group but what if they are all different? Much more work
What about square and rectangle slots that are often determined by the material thickness?
Like a lot of folks I took too long to start using layers, but the more I use them the more benefits I find.
I do still have an issue forgetting to activate the layer I am changing... sure would like a check box for 'the last selected' layer