Why he couldn't leave?

There was a meeting with a large number of people. At first the speaker was very interesting, but as time went on, he became very boring. Finally when he was through, there was only one man sitting in the large room.

　　The speaker walked up to the man and said, "Thank you for hearing me out when all the others left the room."

　　"Oh! Don't mention it!" replied the man, "I cannot leave because I am the next speaker."