You've to know it

"Sorry", "Thank you" and "Excuse me", I think we already common with these terms in life. For me, I almost talk these three terms by every day. And I think they are necessary terms that you must know to use in some particular situations. But then, sometimes I wonder why people do not talk these terms. Are they think these terms actually useless to solve the situation? However, I don't think so. Actually they are useful if you talk to people with sincere, and I think you can make it even prowerful than what you act. For instance, say "thank you" with smile to make people feel the sincere and thankful that you giving to them. I've ever served by a waitress with no manners at all in restaurant. At that moment, I really felt angry with her attitude. This wasn't called as 'service' that we deserved. Manners can mean everything, so-called COMPULSORY we have to know it well.