All things being equal, the simplest solution tends to be the right one -- but not in this case. Graphite pencils are a really bad idea in zero gravity: They can break easily, freeing hazardous splinters (not a problem with gravity, since if you encounter them it's likely to be with your feet -- but without gravity, splinters could easily end up in your eyes), they are flammable (obvious issues here), and when you use them graphite dust is released which (in zero gravity) can end up causing short circuits in electronics.
