Because those upgrades allow you in a normal game better map control and thereby more resources. If you do it right, you force the OKW player to invest in light vehicles, thus delaying his tech.
Without upgrades (especially ambulance) you are going to lose very fast.
With them, I can assume that map control would be 50/50. So you need to pay more just to stay in game, not to gain huge map control.
Still, there is no justification to gain gree healing, nades, upgrades and repairs for OKW.
Relic Entertainment
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