Henchman play an important role in action movies. An intrinsic part of the bad guy boss image is having armed henchmen hobble around in uniforms to deter heroes from their goal. Henchman also fulfill the role of cannon fodder. It should be noted that the majority of henchmen are faceless, by equipping helmets or masks, causing them to lose their individuality and making violence directed towards them appear less important.
If we look at stormtroopers from Star Wars for instance, it is difficult for the viewer to tell if these faceless soldiers are humans, aliens, or robots. In fact, in their technologically advanced universe, they don't even bleed when they are shot or have limbs severed by lightsabers. While watching Luke Skywalker and his gang mow down battalions of stormtroopers with their blasters, the viewer does not feel as much sympathy for stormtroopers as for any other character in the movie that does have a recognizable mug. As soon as the scene changes, dead troopers are immediately forgotten.
Diverting your attention away from Star Wars, a scene from Kill Bill Vol. I exposes what happens when a member of the "Crazy 88's" is unmasked:
At 1:45, we see one of the anonymous henchmen lose his mask while his buddies are being sliced to pieces by the Bride, and we have have a moment of realization when a person's face is revealed. As the viewer, we are suddenly flooded with information: this henchman is unique. He's a young man, scared, and confused. Essentially, he acquires traits that are contradictory to what we associate with henchmen. As soon as he is unmasked, the Yakuza becomes a recognizable person for the audience. For his innocent expression the righteous Bride decides not to harm him. But had he maintained the mask, he would have been eliminated without a second thought.