So that they can award you miles from LHR-DFW rather than LHR-ATL + ATL-DFW.
So that they can fool you into thinking you are flying nonstop (or possibly direct with one stop).
To keep you from being eligible for an upgrade ATL-DFW.
So that it will appear at the top of the list of possible itineraries when you are booking.
Last edited by Snidely Whiplash; Sep 24, 2014 at 10:28 am