I agree completely that the model of characters all competing for control of a scene is accurate (and helpful for writers).

If you observe a table with several real people at a real restaurant or coffee shop, even without being able to hear the conversation, you can see from the body language that there’s a power dynamic. Perhaps one person dominates the situation, while another struggles for a bit of control, and a third person just sits there looking resentful at being excluded by the other two. People don’t go to a restaurant as a group in order to eat; they go to joust.

Any two real people meeting face to face seek ownership of the relationship for that moment, and if there’s no struggle between fictional characters in a scene, the script will not only lack tension and momentum, it will come off as unrealistic. Th conflict may be subtle (we rarely declare our quest for dominance overtly), but it’s typically more important than the actual topic of conversation.

One way to understand the basis of the power play (in real life or fiction) is to ask the question “What is this person’s agenda?” about each of the participants.