Hold baggage is a substantial cost to airlines, the expense of repatriating mishandled bags, which arise for a number of reasons but most commonly due to not having enough staff on duty, is very substantial. Likewise where handling is outsourced (most of BA now) the charges made include what works out to be a charge per bag. Pax moaning about lengthy delays waiting for bags to be delivered is also eliminated. So encouraging people to carry their own goes right along with Alex Cruz's "think of a way to save money every day". Extra time at security is a cost to the airport, not reflected in their charges, and the additional time pax now wait due to screening delays is completely irrelevant to the "save money" brigade.