Why can't they? 

My thought is the Drone Wrangler's job would be to :

1) Operate the Platoon Command Fireteams "special" droids

2) Act as 'medic' for the other platoon drones 

3) Act as tech support / on-the-fly scripting support for the platoon's drones

 

Why not? 

I like the idea of each human being a sort of fire team leader, with 2-5 'automatics' supporting them. 

Pick several depending on the human's role:

               a butterfly sized recon drone

               a dog sized direct-fire , maybe with a laser carbine and point defense systems to limit enemy artil

               a dog sized indirect fire drone, with an AGL and software for both direct and indirect fire

               a dog sized drone with a SAW of some sort

               a mule sized logistics drone with cargo racks 

               a mule sized medical drone with a stretcher 

These would be smart enough to handle basic hand signals, a limited spoken vocabulary, and the ability to read their assigned soldier's designator (scope on rifle, data from combat helmet, whatever)

In combat, the PFC might stop for a moment under cover, aim his rifle at the top of a small tree and whisper "Butterfly", telling the drone where he wanted it to go. When he saw it get close, he'd get quick feed from its sensors, seeing some enemy guys in the gully ahead waiting in ambush.  He'd focus his eyes on that window in his helmet, which the helmet comp would read as selecting the window (from looking at his nerve response) then say "Tell Sarge". Then he'd focus on 3 or 4 points in the gully, saying "tag" each time, then "Grenadier, one HE per tag, shoot." 

Note that he's doing this from cover, not in the midst of the firefight, and his hands never leave his personal weapon. While he's distracted with the Buttefly feed and Grenadier, his Laser Dog is on overwatch, making sure nobody comes up and slugs him in the head with a rock. 

When the enemy notices the Butterfly and their "dog" lases it, the Platoon Droid Wrangler would note it was toast, then tell his mule-sized logistics droid, "Send Private Jones a replacement butterfly". When Jones's Grenadier got low on ammo, the DW would prioriatize and dispatch a reloader. When Jone's Laser Dog takes a hit, the DW checks it over, replaces the damaged module and patches the armor. 

When it really drops in the pot,  the DW brings his two Combat Mules up , one with a VRF Gauss gun and the other with an Rapid Plasma gun...