The charity workers are not intended to symbolize anything but the Christmas spirit. There were many such people who raised money for the poor at Christmastime, and these portly gentlemen were the ones who had been assigned to approach Scrooge and Marley, not knowing that Marley had been dead for seven years. The author wanted to show Scrooge's cold-hearted character before the experiences with the ghosts recorded in the story. And, incidentally, Dickens wanted to make it clear that Marley was dead, because Marley will appear later in the story and will undoubtedly be a ghost.
“Are there no prisons?” asked Scrooge.
“Plenty of prisons,” said the gentleman, laying down the pen again.
“And the Union workhouses?” demanded Scrooge. “Are they still in operation?”
“They are. Still,” returned the gentleman, “I wish I could say they were not.”
“The Treadmill and the Poor Law are in full vigour, then?” said Scrooge.
“Both very busy, sir.”
“Oh! I was afraid, from what you said at first, that something had occurred to stop them in their useful course,” said Scrooge. “I’m very glad to hear it.”
Scrooge, of course, is being disingenuous. He is well aware that all the miserable institutions for the poor are in full operation. Scrooge will undergo a great transformation during his encounters with the ghosts. The change in Scrooge's character is the most important thing in the entire short novel. It is the best Christmas tale ever written. What everyone remembers about it is how Scrooge woke up on Christmas morning a changed man. But Dickens felt it necessary to emphasize his meanness in order to make the transformation that much more dramatically effective. Scrooge is not only selfish and miserly, but he enjoys mocking those who are unable, like himself, to keep themselves warm, comfortable, and well fed. He shows his cruel sense of humor to the two gentlemen who approach him for a donation. It is significant that they know nothing about him. His is just a name on a list of people they have been assigned to call upon. Therefore the effect of Scrooge's personality is more strongly felt by these two callers than it was by Scrooge's nephew, who was also used in this scene to bring out his uncle's selfishness and bad disposition.