...are we sure the ones in that very last pages are medics? They look like they can bend steel.
They could, but that would still make them 2nd/3rd line support like engineers or logistics. And logistics always need more big muscular haulers.
Infantry fighting requires an entire different set of mentality and not everyone is cut out for fighting in the trenches... or engage in front line combat where adrenaline and struggles for life occurs daily. IIRC only 5% to 15% of the modern army is actually "true" infantry, everyone else is a specialist or support role. Think about it, a transporter, armorer, medical, engineering, and food provision - we're looking at 5 groups of supporters to 1 group of fighting component. Factor in taxpayers to pay for all of that, and we're probably looking at 10 (or 100) to 1.
If everyone (or > 25% really) is forced into the role of infantry, we're practically talking meat grinders and/or human waves attack... and that would mean going back to world war 1 tactics or "modern" Russia.