Why Do Customers Think They Can Be Always So Rude??

I felt so depressed today at work… I had just started and this guy wanted to pay with a 50 £ note so I asked him if he had any smaller change, and he went “What’s the magic word???”! He wasn’t try to be funny, he was just being patronising and rude. Fine I didn’t say please but my question was as polite as can be…
Then a family came to buy tickets and the kids started making fun of me because of my name, and the stupid mother was just there and knew that I had heard, but she didn’t say anything!! And then we complain that kids are so rude and bad mannered nowadays!! It really made me sad.