The Russians do luv them some volley guns. To be fair, I think they are pretty cool as well, and are a cheap way to up rate of fire if you already have a bunch of rifles and/or SMGs laying around, as opposed to engineering some new high rate of fire weapon.
The US tends to do the same thing but we strap beltfeds to everything. The UH-1 gunships and M35 Guntrucks of the Vietnam era are one example, 160th SOAR straps a minigun or two to everything they fly, etc. If left alone, soldiers will strap more guns on something.
Heh, real world example: The LCU-2000 class landing craft I used to run came from the factory with two .50 M2 machine guns in tripods for defense. On the ones I ran in CENTCOM for GWOT, we had "uparmed" them by welding more tripods, armor plating, and acquired more guns, so we were running with 2 M2's, 2 Mk19s, a M240B, and 2 M249s, all mounted for vessel defense. We stopped there because we ran out of crew to man the guns.
THen of course there's the Metal Storm the Aussies invented.
https://www.youtube.com/watch?v=d8hlj4EbdsE