Not long ago, I read something about how English-speakers are conditioned to avoid saying "No" directly, but to use body language, tone of voice, and "I'd love to, but..." as a way to politely turn down an invitation. For example:
A: "Would you like to go see Pacific Rim tomorrow afternoon?"
B: "Tomorrow afternoon doesn't work for me. Have fun, though! That movie looks awesome!"
Person B conveys disappointment that tomorrow afternoon and removes herself from the equation without having to say "No." The answer isn't, "No, I don't want to," but, "No, I'd love to, but I can't."
Like most things, this social dance has evolved. How often does this happen to you?
A: "You doing anything tonight?"
A: "Awesome! We should go see Pacific Rim!"
I've done this to people; people have done this to me. It's not a conscious thing. On some level, we are aware that leading with an activity and time will give the other person a chance to come up with an excuse to say no, so we want to circumvent that by leading with the time. If a person agrees to the time, then they can't say "no" to the proposed activity, right?
Obviously, this kind of setup sucks if a current lack of plans is intentional and Person A is not understanding. Some people are cool about it, but some people feel slighted, as if Person B is saying, "Sorry, but sitting on the couch alone sounds more fun than hanging out with you."
This is the sort of thing I think about while I'm falling asleep. I can't wait for Pacific Rim to hit DVD.