The Ghost of Christmas Present: You should have accepted Fred's invitation to dine.
Mr. Ebenezer Scrooge: What?
The Ghost of Christmas Present: For Fran's sake, if not for yours.
Mr. Ebenezer Scrooge: You find my nephew amusing, Cratchit.
Bob Cratchit: He's a very pleasant fellow, sir.
Mr. Ebenezer Scrooge: You're another Christmas lunatic like him.
Bob Cratchit: If you say so, sir.
Mr. Ebenezer Scrooge: Oh, it seems you doubt me, Mr. Cratchit. What are you, then?
Bob Cratchit: Your clerk, Mr. Scrooge.
Mr. Ebenezer Scrooge: My fifteen shilling a week clerk, with a wife and family, but you babble about "Merry Christmas." I'll retire to Bedlam.
Answer: This is really a question for the author, Charles Dickens, but I see it as Marley wanting to put fear and anticipation or suspense into Scrooge. It sets the stage for him to think he's going to have to deal with the horror of these ghosts visits for three nights in a row. But then, after the third ghost, he thinks he's missed Christmas, but in his mind, it was a miracle that the ghosts were able to do it all in one night, making the day even more special.
Bishop73