Picture a bipedal mech with a big gun that looks like rock. It has a shroud for people to hide under, so they can't be seen by thermal imaging. It could allow special forces to exist on mountains undetected for extended periods of time.
Admittedly, a quadruped would be better for traction purposes, but there could be specialized use cases.

Or the Titanfall mechs, that are much smaller than typical and used for industrial purposes, which canonically are used to speed up colonization because they don't need a lot of the infrastructure that wheels need.