Arcing causes more fires, because over current caused all the fires until we tightened standards and dual-mode circuit breakers.

Now fires are caused by loose connections arcing, and damaged wires arcing to flammable material.

Breakers are specifically designed for a sustained current, but arcing is dangerous because it tends to cascade, light arcing damages contacts, leading to more arcing in a cycle.

The real danger of arcing is that it can happen outside of view, and start fires that aren't caught till everything burns down.