Indeed. It's a very strange argument - sidewalks require significantly less to sustain.
For a start, the build quality can be a lot lower - a sidewalk doesn't need to support lorries with 13t loads.
As for maintenance, the damage to them is far less, and repairing a sidewalk would usually be a small diversion rather than the drama of a road closure.
I'm not quite sure why anyone would think sidewalks are an unthinkable burden.