Nooooooooooo

I heard an interview with Deborah Fallows, who recently wrote a book called Dreaming in Chinese: Mandarin Lessons on Life, Love, and Language. It's recently been brought to my attention that it's pretty foolish to make sweeping generalizations about the people in a country that is home to over a billion people - and it would be especially foolish for me. So the author may or may not have a leg to stand on when she says that generally, Mandarin speakers don't say things like please and thank you to their loved ones. She says please and thank you and such are formal words, and would feel cold and stiff if you spoke them to your dad, for instance. She says that, for example, if my mom asks if I want a drink, the English speaker might say "Oh, no thank you, I just had something to drink." A Mandarin speaker, according to the author, would probably say something that would translate to something like "don't want."
I do feel qualified to make sweeping generalizations about the South - I've spent time enough to learn that well-mannered kids are supposed to call grown-ups sir and ma'am, even if those sirs and ma'ams are your parents. At first, I found that off-puttingly formal, but I grew to kind of like it after a while. So much I adopted it when I was working in the group home - I tried to use words of respect to remind myself to respect the people with whom I worked. Most of whom, in retrospect, found it off-puttingly formal.
I've been thinking a lot about the vocabulary of politeness since I heard that interview. As a writer, and even when it comes to public speaking, I'm all about omitting needless words. They gum up the language, obscure meaning, and waste time that could be better spent more substantively. Where does politeness fall in there? Do I really need to preface my McDonald's order with "May I please"?
In the case of McDonald's, the polite words aren't just there as filler. When I worked in food service, I hated how some people treated us like sub-humans whose only purpose in life is to produce food, and to do so entirely without error, or God help you. (If you take nothing else away from your post, take this: the person who just served you cold fries is a human being with an income near the poverty line who probably isn't personally responsible for your fries being cold anyway).
But what about when the person you're may I pleasing isn't a McDonald's cashier. Why do I ask Jeremy "Will you please pass the salt," when I could express my meaning just as effectively by saying "salt"? If we were all to stop saying please and thank you to the people with whom we're familiar, would our worlds be any different? What if parents stopped making their kids say please except around strangers? Maybe we say please and thank you to our loved ones just to stay in the habit, so we don't forget to use them when strangers offer us beverages?
I'd experiment, but it would seem rude.