Ha! I've noticed this too. And, no, I don't think this represents what is common in the U.S. I always say "catch ya later; bye" or something like it--and everyone I know does as well. I will say this: I have found people who don't always greet you on the phone at the beginning of the conversation. There are a few people I know who do this, but one in particular. It'll go something like this...
ME: Hello
HIM: Soooo I was reading something in the paper that I thought was pretty interesting.
ME: Okay...
HIM: I understand you won Best of Show at the latest ADDY Awards.
ME: Dallas, is that you?
HIM: That's two years in a row, isn't it?
ME: (mocking) Hey, Dallas, nice to hear from you. Yes, this is Jon, and I'm doing good too.
HIM: I'm just saying that a guy who wins Best of Show two years in a row could start to get a big head; wouldn't you say?
ME: (sigh)