Love "is not rude (unmannerly) and does not act unbecomingly" (1 Cor. 13:5). It is amazing how the words please or thank you can soften a command. Those who have authority and are in a position to tell others what to do could avoid a lot of rebellion by using better manners.
For relationships to remain harmonious, we need to treat each other with courtesy. We need to engage in the pleasantries of life. They may not be vital, but it's wise to use them because they can prevent tension and rebellion.
Courtesy is also vital in our relationships with our family and friends. We have a tendency to take liberties with those closest to us that we wouldn't consider taking with a total stranger. A lot of strife can be avoided by simple courtesy.
H/T: Conflict Free Living by Joyce Meyer