When I'm building a fire I crumple the newspaper into a ball because it increases the surface area and density of the fuel, so it will burn longer and hopefully catch the wood on fire
I'm just using it to start a fire, so the efficiency isn't really important. What I need is a couple minutes of hot flame that will light other things on fire.
it also ruins the piece of paper, so you can't make revisions and keep working with it.. nothing can be done with what's on that page.. it's all garbage!
If you get frustrated by something you're writing, crumpling it into a ball gets out frustration by destroying the work and then it's easier to toss into a garbage can.