A film is almost never shot in the order the audience sees it. The schedule is built around cost, and story sequence is one of the first things sacrificed to it.
Locations are the organising principle
Moving a production is expensive, involving transport, permits, lighting setups and often road closures. Every scene at a given location is therefore shot together regardless of where it falls in the story.
A character may film their first and final appearances in a room on the same afternoon, separated in the story by an hour of narrative development.
The saving is substantial, since a company move can consume most of a shooting day. Schedules are drafted by grouping locations first and then fitting the story around them.
Cast availability compresses the plan
Actors are contracted for a defined number of days, and a well-known performer may be available only in a narrow window between other commitments.
All of their scenes are then compressed into that window, which can mean shooting emotionally unconnected material back to back with no chance to build up to it.
Child performers and animals carry legal limits on working hours, which constrains scheduling further and often decides the order of an entire sequence.
Continuity becomes a documentation task
Because scenes are recorded out of sequence, someone must track the state of every element: costume, injuries, hair length, the level of liquid in a glass, the time of day implied.
This is recorded in detail and photographed, since a scene may be picked up weeks later and must match footage already shot. Errors are expensive to fix afterwards.
Directors sometimes shoot a sequence in order deliberately where a performance depends on accumulated emotion, and the decision is a recognised budget cost rather than a default.
Performances are built in fragments
An actor must know precisely where a character sits emotionally in each take without having played the intervening material, which is the main craft demand the system creates.
Directors support this with detailed breakdowns of the emotional arc, and rehearsal in sequence before shooting begins is common for the same reason.
The fragmentation is also why coverage matters, since alternative readings of a scene give the editor room to adjust an arc that only becomes visible once assembled.
The edit reconstructs the story
Editing is where the intended order is imposed for the first time, and problems in the arc surface there rather than on set, when reshoots are costly.
Scenes are frequently moved, and a sequence shot as one moment can end up split across the film. The written order is a proposal rather than a fixed structure.
That flexibility is the compensation for shooting out of sequence. The schedule saved money on set and handed the edit an unusual amount of freedom over the result.