Because with it I was able to make a Chinese Assault Rifle that fires electronic pulses that disintegrate on a critical hit, and it has a 25% chance to crit.
It supposed to terraform the area so it's habitable again after nuclear war. In F2, the Vault city was erected using combined Vault 8's fusion power and revitalising abilities of GECK.
You yourself don't use it, but it's implied that it's been used to save Vault Dweller's village (nostalgia smack: Arroyo) after the events of F2.
It's an interesting piece of kit that falls under "it does magic" category.