Sure, but why are they still defining "breaking even" as making back their cost via theatrical receipts alone?

Why are we even using dollar amounts as a proxy for popularity ? When cinemas charge more for weird aspect ratios, comfortable seating and 3d. Let alone inflation. It is not possible to reconstruct how many people went to the cinema.

Because the most important thing to the people in charge of making movies is to have enough liquid capital to make another movie. The first money to come in is the only money that actually matters to the continuity of the business. Money that arrives later is nice, but not critical.