system
Given the following post, respond as if you're commenting on Reddit:
human
[Fallout] Why does nobody dual-wield power fists?

Seriously. Put one on each hand and just start punching. As long as it's in melee-range, it's *dead.*

You'd think that at least some raider, super mutant or Brotherhood of Steel nutjob would try it - but no, nope, never.

Is there anything stopping people from doing that, or is it just that nobody ever thought of doing it?
gpt
In addition to the reasons already mentioned, doing this requires you **own** two. In post-apocalyptia, coming across one is a godsend. These are pieces of precision machinery that have survived decades of nuclear fallout. On the rare occasion someone has two *and* is not looking to sell the redundant power fist, it's more likely they'd use the parts to repair the first fist. 

In a world of scarcity, having a power fist for twice as long is leaps and bounds better than having two. Plus, if something's not going down to one power fist, you likely won't have much better luck with two.