I haven't seen earpieces since they brought in the guests from the "studio" in...wherever the heck it was. Although they might have had them at the last selection.
Usually those are used to hear what a person or people at a remote feed are saying. (So it's possible, even probable, that they had the earpieces on when the girls were watching backstage, etc.)
You'll notice when there's a show like that, and people are fed lines, it's almost stilted-it takes a minute for the person with the earpiece to get the message and often it's out of context. It's hard to listen and talk at the same time. Not impossible, but very hard. That's why most shows still use cue cards and teleprompters.