Say What?

Where did the phrase "practicing common courtesy" come from? I have truly been on a kick about this lately as I clean at my job. I'm pretty sure that phrase is not seen or used as often because I find that for most people, courtesy, is NOT common. How sad, and how did we get this way? Was I one of the only people in the world taught to push my chair in when I got up from the table, desk, wherever? Was I the only one who was taught that if you drop something, you pick it up...not leave it for someone to pick/hang up again? It has blown my mind lately how much people, even in a church, expect someone else to clean up after them...the sad thing is that I'm NOT talking about the children. I almost expect it out of them, BUT they are learning, and in some cases, unfortunately so. It's adults! And it makes me sad and angry...
While growing up I was raised in many small churches. We had "janitors" I'm sure, but I don't remember them being there all the time to clean up after us. I remember having to wipe tables down after I used them, pick or SWEEP things up off of the floor, and I got in SO much trouble if I went into a classroom and didn't put things back where they went. So I learned to do all these things. I know how to say "please" and "thank you", although recently I realized that instead of saying "you're welcome" I say "yep" and thought, "Is that rude? OK, I will make a conscious effort to say 'You're welcome!" And so I have. I hold the door for people when they are walking in/out, I pick up trash off of the playground instead of walking over it and hoping someone else will get it. Isn't this what we should all do? Isn't this "common courtesy?" I guess I just take it as natural instinct. I don't get adult behavior any more.
So I plead with people. Help teach your children what common courtesy is...have them ask to be excused from the table, and automatically take their plates over. Do NOT allow them to talk back to ANY adult (as I have experienced much of...and I don't blame the teachers!) These are common manners...common courtesy...that's just not so common any more.