Why did my parents bother teaching me manners? From good morning, good afternoon, good evening and good night to sorry, please, thank you, I had it up to my ears whilst growing up. Watch how you speak to people. Wish them. Be polite. The same story in school. Good manners apparently, were drilled into our small brains.
When it comes to present day usage of good manners, I have found that politeness comes at a price. When most courteous and pleasant, often, you are considered an ilichavai (grinning mouth -- a push over?). If you are polite, it does not necessarily mean you will get politeness back. In fact, people may even snap or be curt or take you for a ride.
So I have learned to test the waters. I will be polite at first as I have been taught to be and then when I see the waters are rippled or choppy, I do some choppy talk of my own. Speaking then becomes barking with an odd snap here and there. Very dog like behaviour. Can't say it helps matters as such. But it sure does get people's attention and they know that they need to watch their mouths with me.
However, downright losing of temper never never helps. That never accomplishes anything. But if people know that you are on the verge of losing it or are terribly capable of losing it, you can get things done.
Sad but true. Being grouchy helps in many areas. But I am an optimist. I will stay pleasant until pushed. It is after all so easy to be snappy and more tough to be sweet.
Oh, and sarcasm helps. A relief for yourself while the mannerless one is stumped ...at least temporarily!