Almost no film is shot in the order audiences watch it. The schedule is assembled around what is expensive and immovable, and narrative sequence is not on that list.
Locations are grouped, not revisited
Securing a location involves permits, insurance, neighborhood notification and payment for the time occupied. Returning to the same place twice means paying that cost twice.
So every scene set in a given location is filmed while the production is there, regardless of where those scenes fall in the story. A first-act scene and a climax may shoot the same afternoon.
The same logic applies to constructed sets, which occupy stage space that other productions are waiting for and which cost money for every day they stand.
Cast availability constrains everything
Actors are contracted for a defined number of days, and performers with other commitments may be available only within specific windows.
Scheduling therefore clusters an actor's scenes into their available block, which can mean shooting the beginning and end of a character's arc within days of each other.
The scheduling software used in production exists largely to solve this problem, reconciling location, cast, equipment and daylight constraints into a workable order.
Light and weather impose their own order
Exterior scenes depend on conditions no one controls, so schedules typically include cover sets, interior scenes ready to shoot if the weather turns.
Scenes requiring particular light have narrow daily windows, which means a sequence that reads as continuous may be assembled from several days of shooting at the same hour.
Night work carries higher costs and stricter turnaround requirements for crew, so night scenes are grouped to minimize how often the whole unit flips its schedule.
Continuity is a full-time job
Shooting out of order creates enormous scope for inconsistency in wardrobe, props, injuries, hair length and the exact position of objects between shots.
A script supervisor tracks all of it, documenting what was worn, where things sat and how each take played, so that scenes filmed weeks apart cut together.
Performance continuity is the harder part, since an actor may need to play a moment that follows an emotional scene they will not shoot for another month.
The edit restores the sequence
Footage arrives in the cutting room organized by scene and take rather than by story order, and editing assembles it into the intended sequence.
Because scenes exist independently, the edit can also reorder them, and films sometimes change structure substantially from what the script specified.
This flexibility is a direct consequence of the shooting method. A production that filmed strictly in sequence would have far less room to restructure afterward.