We aren't expected to agree with every rule WN has, but if you use the service you are still bound by the rules you agreed to. Otherwise, there are other airlines available.

I actually don't really see why WN would care all that much if the CP holder didn't fly, if their systems could make sure not to give the funds back. I mean, I'm sure they'd prefer to sell the companion a walk up fare instead, but I feel like it's gotta be a rareish use case. If the primary passenger didn't actually expect to fly, you'd figure most people would just book the companion their own flight initially instead.