This is what the staff person in the LAX Metropolitan Lounge was telling people. [I was in there for 11 hours.] She made it sound mandatory. One passenger balked and refused, saying that he had never been told before that checking luggage was a requirement. When asked why, the staff person said that it leaves space in the luggage rack for people getting on later at stations where there is no checked baggage. And her other constant sentence to passengers: "Tip your redcap" [which I'm sure the redcaps appreciate!]. I found the whole thing bizarre.