What use is the reference node in nodal analysis?
The point is just to make the math easier. Generally "ground" is going to have the most elements and will therefore be chosen as the reference node. Try writing out the equations for a large circuit by first following the guidelines above, and then next without following the guidelines. You'll find one is a lot easier.

As far as I know it is only for mathematical/notational simplicity, there is no electrical or physical significance to the node you choose as your reference node.