Is using a grid cheating?

I recently visited the Thielska Gallery here in Stockholm. It is a small museum but there are some real Swedish gems to see. Anders Zorn, Eugéne Jansson, Bruno Liljefors and Carl Larsson. It was Larsson's pencil portrait that interested me most, I was surprised to see he was using the grid system to draw his portrait. So the question remains, is it ok to use a grid while drawing?

Carl Larsson