The power of because

To ask for a dime just outside a telephone booth is less than to ask for a dime for no apparent reason in the middle of the street.

-Penelope Brown & Stephen Levinson, Politeness

The opening quote seems to be true. It raises the question of why, though. An economist might say a gift of 10 cents is a gift of 10 cents. You are short 10 cents no matter what the requestee's reason. So why should it matter?

The power of because?
Empirically, in a well-known experiment, Ellen Langer and colleagues showed that 95% of people standing in line to use a copy machine were willing to let another cut in line as long as the cutter offered a reason, even if that reason was inane (e.g. "because I have to make copies.")

The explanation given by Langer and colleagues was that people are primed to do defer to somebody who provides a reason. Thus, the word "because" essentially in and of itself can manipulate others. This not only causes us to give money to people who need it to make a phone call, but to simply give money to anybody who gives a reason.

I haven't been able to find the original research paper -- it seems to have perhaps been reported in a book, not in a published article -- so I don't know for sure exactly what conditions were used. However, none of the media reports I have read (such as this one) mention the perhaps the most important control: a condition in which the cutter gives no excuse and does not use the word "because."

What are other possible explanations?
Other possible explanations are that people are simply reluctant to say 'no,' especially if the request is made in earnest.

There are a couple reasons this could be true. People might be pushovers. They might also simply have been taught to be very polite.

Something that strikes me more likely is that most people avoid unnecessary confrontation. Confrontation is always risky. It can escalate into a situation where somebody gets hurt. Certainly, violent confrontations have been started over less than conflicting desires to use the same copier.

Speculation

None of these speculations, however, explain the opening quote. Perhaps there is an answer out there, and if anybody has come across it, please comment away.