Because it would undercut their ability to dynamically control pricing systemwide. All hospitality businesses, with the ubiquity of big data, are moving towards the endgame - the point where every available seat/room/etc. is sold for the last marginal dollar that it will command. Reliably giving out upgrades prevents people who might otherwise buy a higher room class from pulling that trigger. It is training the customer - we are seeing the airlines starting to have success with it, where they are selling more J/F outright to folks who use to sit in those seat on a Y ticket.