The specific answer, although it may seem unsatisfying, is that it is a narrative technique.
"Flashbacks", for instance, are a staple of cinema, and used to reveal hidden information that makes sense of and adds emotional weight to the present action.
My recollection of the movie is that Sorkin expertly used this device to add emotional impact and "dimensionality" to the biopic.
Quentin Tarantino famously commented on the inadequacy of purely linear time in cinematic narrative, and mentions novels as being a form not always bounded by linear story progression. Tarantino uses both flashbacks and asynchronous story structure in such films as Kill Bill and Pulp Fiction.