I think as of right now, many chassis are mostly only being looked at for what weight/energy capacity they have which tends to leave many unused or forgotten. I feel like by adding a passive to chassis players can start to think of more unique way to building robots as opposed to just running the same Purifier/Cyclops/Raven setups all the time.
Here are a couple of example:
Fenrir Legs: Bloodhunt
Robot modules you put into a critical state allow you to have a temporary move speed when approaching them for a few seconds
Pursuer Legs: Parkour
Allows you to perform an angled wall run maneuver, doing so costs fuel during its usage
Scorpion: Scurry
Dashes you make to the side are much faster and snappy (think Volta dash), but it has an increased fuel usage compared to regular dashes
Cyclops: Tenacity
When one of your legs break, the robot goes on a limping state where it prevents the robot from immediate death, but it has 10 seconds before the robot proceeds to destruct (or the other modules go to zero as well)