Proper Etiquette?

Whatever happened to good manners? Have people in today's society forgotten how to give a friendly smile, say please and thank you, and other pleasantries? And what about even the people we know? Our friends, neighbors, and family? I just had to get this off my chest and ask for your opinion: if you show up unannounced at someones home as they are about to sit down for dinner and then linger about until you are given an invite to the table....wouldn't it be polite to not only say thanks for the meal, but to offer to clear the table, help put food away, or even help with the dish washing afterward? I would certainly think so, but nooooo! We are busy, busy, people. We have time to impose ourselves into someones home and dinner table and then when the meal is over we are out the door with barely a thank you coming from our mouths. I can honestly say, as an adult woman I have never been a guest for dinner in someones home and have not offered to clean up afterwards or help with the dishes. What about you? I bite my tongue because it hardly seems worth an argument but next time, I may just be tempted to throw my dish towel at them and point them in the direction of the sink. And it also wouldn't be a big deal if this scenario hadn't started to become an annoying pattern. I just don't know where people get their nerve and complete lack of consideration. Ok, ok, I'm done venting and I feel better, but c'mon people, get some manners!!!