Maybe they are concerned. And maybe it only happens once a day or once a week - and it just not worth worrying about during NORMAL checkin. When the count is off, they handle it. Or maybe if so infrequent, not even worth it. (even though it is against some federal rule - probably FAA or TSA). As you say, it is minimal if any revenue loss. They fly 28,000 flights a week, sometimes stuff happens.

Personal note: I would be hard pressed to try to beat this myself and risk the loss of companion pass, and maybe all points, and maybe never flying SW again. Just me.

Where in that CFR does it state that holding a boarding document in your own name is a requirement? That CFR is about screening of passengers. The passenger has already been screened for weapons, explosives, etc., and presumably had a boarding pass in their own name at that point. Matching the name to the name on the BP was always about revenue protection and for the most part, still is. If airlines truly were concerned about bp's matching ID's, they'd check ID's at the gate. That they don't suggests that the risk to them, either revenue or security related, is mostly non-existent.

Ultimately I don't think it is a zero revenue loss for a couple of reasons. First, they'd have to be able to sell that extra seat in the last few minutes before the flight left. WN doesn't overbook anymore so they can't sell it ahead of time as an overbooking. Second, if I wanted to fly A to B and my companion wanted to fly C to D, then booking my ticket C to D along with my companion, but then not showing and buying a ticket for me from A to B has resulted in lost revenue on the C to D ticket that the companion would otherwise have paid for. In other words, people could effectively never buy a ticket for their companion. That would be ok if the pass holder wasn't flying on another flight. WN is willing to let the companion fly free as long as the pass holder accompanies them. Turning a blind eye to a companion flying without the pass holder opens up a world of abuse of the program and therefore monetary loss to WN.

If Southwest were stupid enough to let Companions fly free without the CP holder on the plane, they would need to change the name of the benefit to "Friends Fly Free" (FFF instead of CP?) They would also have to double the number of flights required (possibly more) to get the FFF benefit since it's worth a lot more to the passenger.

A poll -- how many CP holders would like Southwest to be stupid and turn it into a FFF benefit but you have to take twice as many flights? Anyone???

I don’t have physical proof but this happened to my colleague in 2016.

Wife on companion pass boarded while while he did not board. They came onboard to ask her to identify herself and get her bags to come upfront. They mentioned the companion pass holder was not onboard and they will offload her. The flight was closed then so buying a ticket on the spot was not possible. The husband ended up buying a last minute ticket on UA to get her home.

There is some missing logic here. Letting the companion fly free is still the companion. It is still limited to ONE SPECIFIC person. There is no "Friends" involved at all. Nobody asked about letting a friend fly. One person BOUGHT a ticket, and was going to still PAY for the ticket even if they did not fly. The legitimate companion still wanted to fly.

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.