There are places where business phone etiquette is obviously a thing of the past. This is probably because many people have not been trained in using proper etiquette of any kind, let alone on the phone at work.
Certainly, some calls are more informal than others, but basic civility is still the order of the day. It's saying, "This is the accounting office. How may I help you?" or "Thank you for holding, ma'am. I'll transfer your call now." Or, "I'm sorry you've been transferred so many times. Let me call the number and I'll stay on the line until someone answers."
You want to get under my skin? Answer my questions with "Mm-hmm" or "Uh, huh." So rude. Anyone who uses a business phone line should be trained in phone etiquette.