Please and Thank You

When you eat out, do you ever pay more than the expected 15% tip? Was the service average? Good? Better than you expected? Even so, would you pay more had the service been praise-worthy? Diners frequently disrespect servers as if they aren't even people. A tired server in all situations must be friendly, hospitable, helpful, and courteous. You can only be so kind and honor the server the same way you're being treated. Fair and square. There are those who try to get away with tipping nothing or simply tipping undeserving amounts. I want to throw the food that was brought to them in their faces and to never allow them back into the restaurant.
Why are people condescending to service workers? Does it make them feel better about themselves? How can people be such assholes? I've witnessed many younger, if not middle-aged folks, remain seated on the train when there's an elderly person, pregnant woman, child, or simply a man/woman with many grocery bags standing by them. Do we not know common courtesy anymore? Certainly people hardly say 'excuse me' or 'please and thank you.' Maybe we need to go back in time and have manners and simple respect for other people beaten into us like my parents did when I was younger. I think it was rather effective.
Just today, I witnessed a six-year old reprimand his grandfather and called him 'crazy' and 'stupid.' His parents sat idly by and said nothing. I was in awe and my jaw dropped. They simply did nothing. If I was his parents, I'd pull him outside and give him a nice beating. Kids these days are spoiled rotten and take everything for granted. What's wrong with the world we live in? What's happening to all the good people that used to exist? What will it take for everyone to live peacefully with one another and do good deeds?
Thus far, the ideal is far from the reality.