Except, that's your only thing that you can use to deploy to deny territory. And it doesn't do it in the same way an artillery piece does.
Outside of the Schwer OKW's defensive options are kinda limited due to the Flak Emplacement being utter trash (and expensive for what it does), and sandbags dying to easy. It's always more rewarding for OKW players to play very aggressive.
Its almost like potent, offensive arty offmaps, lack of defensive tools, lack of campy on map arty seems to be creating one coherent army.
Its almost like OKW is designed not to defend and hold territories, but like an army that is suppose to press and push against them.
If I wouldn't know better, I would say OKW army is made the way to make it offensive army with slow start and strong snowball effect, like its themed after certain war period, maybe even certain campaign/battle.
If I was to guess, I would say they might have been made and themed in such way that they would remind of ardenes assault where germans were using intense arty barrages(off maps, specifically pfusilier doc one) right before the attack and where germans were offensive, not defensive.