You are really underselling their firepower. Yeah, having 4 models with the same weapon makes their DPS drop, but their weapons are basically 4 improved Bars and compared to Volks STG, they have basically double the damage at long range.
My point is not that they are bad per sé, but that they don't serve a distinct role. Yes, their long range DPS is much higher than Volks but if I want a long range squad, I'll take some LMG Obers who are cheaper, with higher long range DPS and who benefit from the sustained DPS by having most of it coming from 1 transferable LMG.
Then medium range is already covered by the much more efficient Volksgrenaders with STGs of which you'll have 3-4 squads by default anyway.
Then if you want a CQC squad, you're much better off with STG44 Obers because once again, they are cheaper, with much higher near DPS and they benefit from the sustained DPS by having most of it coming from the 2 transferable STGs.
Which leaves the Falls with nothing special really. They simply do not really have anything to stand out. Which is why I never use them and I rarely see them used by other players.