Continuity mistake: At the beginning of the film when ARIA gives a 36% match to the terrorist being tracked, one of the Soldiers throws a small prop driven UAV to get visual identification. Before visual identification is attempted, the screen at the NMCC already states a 51% match BEFORE the visual identification is compiled by the computer and then told to the SECDEF. ARIA didn't change the match percentage until AFTER she ran the visual identification program.
Continuity mistake: When the Porsche Cayenne is racing through the junk yard, in one shot the right headlamp is broken. In the next, it is fine again and then it's broken once more.
Continuity mistake: The wounds on agent Thomas's forehead that got in bridge crash change position several shots later.
Continuity mistake: The wounds on Jerry's forehead change position through the film.
Continuity mistake: When Jerry discovers the deliveries to his apartment and takes the gun out of its wrapper, in the first shot he's holding it quite loosely in his hand, then the angle changes and his fingers are wrapped tightly around the grip. (00:17:20)
Answer: I think it was to show that Jerry and Rachel maintained a friendship after it all. Also to maybe, maybe hint about some kind of romantic future in the way that Rachel says, "you remembered", when her ex-husband was said to never have remembered Sam's birthday.That's my thoughts - I think it's just to let us know how the characters turned out.