Yes, typically the savings would be in the weight and physical size of the wiring harness (as well as possibly allowing for tighter bend radii). You'd design for a max amount of heat generated by the wiring harness, or possibly a max voltage drop if that's a constraint. You don't need to do heat dissipation calculations yourself, there are standards like SAE AS50881 that do the heavy lifting for you.

Edit: Smaller wire is also cheaper of course. That's probably a pretty significant upside when talking about a mass-produced vehicle.