I think the whole "don't draw anything on layer 0" thing is a hangover from AutoCAD.

People start out drawing everything on layer 0 because they don't know about layers and cope OK. Later you start using layers so you can turn things on and off. You might have various reasons for doing this. As long as you understand the principle of layers, how to move things from one to another and what you can do with them, it doesn't matter as long as it works for you throughout your design process.