Young people these days are not trained in etiquette.
It is impolite to address elders by their first name unless they say it's ok. Doubly so for a customer. If they introduce themselves to you by first name it's good. If I introduce myself as "Mr. Zoid," then it's disrespectful to address me by anything else.
Restaurants are particularly bad. My skin crawls when a server refers to my wife and me as "you guys." On top of that, the wait staff will invariably interrupt conversation at the table.
The polite thing to do is to stand quietly and wait for a break. My tip subtractor goes into high gear when a server interrupts my wife and me in the middle of a conversation.
I have worked in many service jobs and I understand how it works. If someone wants my respect (and my money) they have to show me that they understand how it works, too.
So do you give less tip when it comes to gender and looks?