I don't really understand why everyone wants the StG-upgrade for Volks to be a role changing upgrade, when the BAR for Riflemen isn't one either, especially as the effect of the StGs is much less an issue (even compared to only one BAR, which costs less).
Well, the thing is USF don't have any late-game non-doc Elite infantry like OKW has. They have to rely on Rifleman throughout the match (Lieutenant and Captain are very much a more specialized Rifleman squad) and they're rewarded for keeping them alive and upgraded. If you manage to wipe out USF's Rifleman, they'll just slowly falling apart and die (Kinda like how OKW was when they relied heavily on Volks' Schreck blobs. Without the blob, the faction was pretty much dead). However, with OKW now, they actually do have an Elite late-game infantry (Obersoldaten)! Yet, no one used them cause they're playing OKW the similar way they play USF: rely heavily on mainline troops, despite Volks are actually weaker and less utilities compared to Rifleman. OKW needs other late-game units to combat Rifleman and Obers are 1 of them!