Inception is a movie about many things, but primarily it’s a movie about telling stories. And for both GMs and game designers, what I consider the most important scene in the entire movie is the one where Cobb hands Ariadne a block of graph paper and asks her to show him a demonstration of her creative abilities as an architect. And none of the mazes she draws for him are satisfactory until she flips over the block and uses the plain backside instead of the graph paper.
If you are playing on a battle grid and want to be able to exactly determine the number of squares in any given room, you can still copy or trace the map onto graph paper. But other than modern houses, the world is not arranged along neatly places squares. Trying to create maps for forests or caves, and even villages or castles along the grid of graph paper never really gets you anything that looks really good.
But once you ditch the grid all kinds of new possibilities become open to you. Which can result in such awesome maps as the ones made by Kevin Camplell presented at Dyson’s Dodecahedron.