Are people normally rude here?

It’s honestly sad how often I’ve watched grown adults act worse than children toward customer service workers in Port St. Lucie. I’ve seen people throw fits over coffee, argue with employees who are just doing their jobs, and treat workers like they’re beneath them.
I’ve even stepped in once because the way a customer was speaking to an employee crossed a line, and I left an extra tip afterward because I felt so bad for the staff. I’ve seen it often enough that it’s hard to ignore. What makes people think it’s okay to treat someone with that level of disrespect just because they’re behind a counter? Service workers are people, too.