It is a mark from the composer to the conductor: Hold the pause as long as you like.
When we finally have the attention of an audience, our instinct is to rush. Attention is precious, please don't stare, okay, I'm hurrying, there, I'm done.
It doesn't have to work that way.
If you've got something to say, say it. Slowly. With effect. The audience isn't going anywhere. At least not the people you care about.
No, don't waste their time. Yes, handle your message with the respect it deserves.
If you have to rush to say it, it might not be worth saying.