There has to be a reason to use them. If they are just like armored cars or light tanks, what's the point? Beyong aesthetics orcourse.
Granted, this is all dieselpunk tech, but in game terms this is how we've used Gearkrieg combat mecha. They are equivalent to armored cars and light tanks, but they can maneuver through restricting terrain that wheeled and tracked vehicles cannot -- wooded areas, rubble, steep slopes, etc. This allows them to bring the benefits of AFVs to places normally not possible.
1. Fire support: Imagine in the rubble choked streets of Stalingrad if a light assault gun could 'walk" along with infantry to provide support, or ascend a steep slope and use an AT gun on advancing enemy forces.
2. Rapid flanking through restricted terrain: the combat walker could move through restricted terrain for scouting or attack purposes, and retreat back through that terrain leaving traditional AFVs unable to follow.
3. Non-traditional attacks: In Gear Krieg most combat walkers can "transform" from walking mode (standing up) to travel mode (legs folded up for travel). In one fun game a US player realized his combat walker could "stand" up and peek over a Normandy hedgerow and fire at surprised German units, get a partial cover bonus and then retract his legs back to vehicle mode for travel. He then would scoot off, pop back up and fire, repeat, etc. It drove the German player nuts!
So there are some advantages to combat walkers...and they look cool!!