Question for the USA folk

[emmaco]

In American movies and TV shows, a person on the phone often hangs up without saying goodbye as soon as the substance of the call is over. Is this the case in reality? Or is it just to make the show quicker? It's considered rude here to hang up without saying goodbye and I have long been curious to know if that's not the case in the USA. Can anyone help clear up this pressing question?

OK, and the icon has nothing to do with the question. I just wanted to use it :)