Branching dialogue appears to multiply endlessly, and in practice it is tightly bounded. Three production constraints determine how much branching a game can afford.
Every branch must be recorded and translated
Voiced dialogue costs studio time per line, and lines heard by a small fraction of players cost the same as lines heard by everyone.
Localisation multiplies that by the number of supported languages, so a branch that adds twenty lines adds them repeatedly across the whole release.
This is the single largest reason branches converge. A conversation that splits and rejoins keeps the choice while limiting the volume of unique material required.
State has to be tracked and honoured later
A choice that matters must be recorded and then respected by every subsequent scene that could reasonably acknowledge it. Each flag adds combinations to test.
Two independent decisions produce four states, and ten produce a number no team can validate by playing. Testing cost grows much faster than writing cost.
Writers therefore work with a small number of tracked variables and let most choices affect only the immediate exchange, which is why so many decisions feel weightless afterwards.
The illusion is maintained by tone rather than outcome
A common technique keeps the outcome fixed while varying how the player character expresses it, so the player selects a manner rather than a result.
This is cheap, because the scene that follows does not change, and it satisfies a large part of what players want from dialogue, which is to play a character consistently.
It becomes unsatisfying when options are labelled in ways that promise more than they deliver, which is why paraphrased choice labels attract criticism.
Structure is designed before lines are written
Writers usually build the graph first, deciding where the conversation splits and rejoins and which nodes are gated by earlier decisions or by character attributes.
Only then is prose written into the nodes, because the shape determines how many lines each path can afford and where reused lines must fit.
This is the opposite of how prose is normally written, and it is why game writing is often described as a structural discipline before a literary one.
Reactivity is concentrated deliberately
Because branching is limited, teams choose a small number of decisions to carry real weight and build the game's memory around those.
Games with a reputation for responsiveness usually did not branch more; they placed their branches where players were most likely to notice and to test them.
The remaining choices exist to maintain the character the player is performing, which is a genuine function even when the world does not change in response.