What's My Line?

Many weeks ago, I was doing some thumb exercises with my remote control when I came across an awards show on TV. I want to say it was the Golden Globes but I'm not for sure. I'm confident you've seen shows like this. A number of awards are presented one at a time, with several nominations mentioned prior to each one.

As I watched, I noticed something that left me bewildered. For each award, two actors would come to the podium and engage in some brief small talk. This would usually include a corny joke of some kind. It's obvious that this dialogue is scripted. In fact, it looks like these folks are reading their lines off a cue card or a teleprompter or something.

So I'm left to ponder the following question. If these folks are actors, people whose job requires them to memorize lines, why can't they actually memorize lines or at least act like they have?