Politeness Theory, as codified by Penelope Brown and Stephen Levinson in 1978, states that persons will attempt use certain techniques to save "face" in the event of acts described as "face-threatening." "Face," in this context, is an expression of self-image denoting personal dignity, respect, or reputation.
Early models of politeness theory rested face-saving and face-threatening on three principles: Power, Social Distance, and Ranked Extremity (Wikipedia). These models have been modified as cultural norms change (monarchies vs. democracies, serfdom vs. freedom), but the roots of the theory remain the same.
Power, in this context, is the authority of the speaker over the listener. If the person attempting to save face is weaker than the threatening person, the face-saving act will be different in tone and purpose than if the situation is reversed.
Social Distance covers both the cultural differences in social class (e.g. rich vs. poor) and the familiarity of the two parties. A person will use different techniques dealing with family than with an employer or employee.
Ranked Extremity is the actual severity of the act; in some situations, where a more polite request would be appropriate, the speaker might use more forceful language to impress the importance of the request. Similarly, if the face-saving act is a heavy imposition, the request might be couched in soothing terms to make it more acceptable.