Favors and fear
I believe that people always want something, when they speak—even if it’s broad or underspecified. That you, the addressee, are included in that plan, as a subject of their wanting.
But I also see a common and easy pitfall, to this way of thinking, which is to systematically overestimate the scale of what people are after. Your cocktail interlocutor might just want you to take over the conversation, because they’re running out of things to say, or they’re anxious they’ve have been talking too much. Someone who starts complaining about their personal life may want emotional support, or sympathy, or brainstorming, or a full-blown serious favor.
Just because communication is motivated, and motivated towards altering others’ behavior, doesn’t mean the ask is as high as one may be dreading.