system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] At the duel on mustafar why doesn't one side just start force flinging lava at the other?
gpt
Because of a variety of reasons.

One, because that takes concentration and effort, which their opponent isn't going to give them when they're in range of a lightsaber.

Two, because Anakin is clearly not thinking about using the environment as a weapon.

Three, because despite everything, Obi-Wan still is trying to stop his friend from becoming a monster, he's not trying to destroy him.

We already saw what would happen if the two fought a Force-battle against each other, and it came out pretty much evenly. A Force battle using lava would just be the same, but with lava.