Charles Dickens believed that people needed to stand up and take notice of the conditions of the poor.  He wrote A Christmas Carol in order to help them see the poor as human beings deserving of dignity and respect.  When I think of your question, two quotes pop out at me.  The first is one of my favorites from the book.  When Scrooge asks why the ghost is there, Marley answers:

“It is required of every man,” the Ghost returned, “that the spirit within him should walk abroad among his fellowmen, and travel far and wide; and if that spirit goes not forth in life, it is condemned to do so after death. It is doomed to wander through the world—oh, woe is me!—and witness what it cannot share, but might have shared on earth, and turned to happiness!”

This demonstrates Dickens's purpose in telling this story.  He wants to convince people to care about others, and feel for them.

The second example that suggests that Dickens felt that society was responsible for the poor happens in a conversation with the Ghost of Christmas Present.  Scrooge expressed earlier that he believes that the poor should go to prisons and workhouses.  After they finish observing the present, Scrooge notices that the ghost has aged and then realizes that there are children under his robes.  Scrooge is surprised and horrified at the sight of them, because they are neglected.  The Ghost of Christmas Present throws Scrooge's words back at him when he asks who will care for the children, Ignorance and Want:

"This boy is Ignorance. This girl is Want. Beware them both, and all of their degree; but most of all beware this boy, for on his brow I see that written which is Doom, unless the writing be erased. Deny it!” cried the Spirit, stretching out its hand towards the city. “Slander those who tell it ye! Admit it for your factious purposes, and make it worse! And bide the end!”

Dickens reinforces the idea that protecting the children, eliminating ignorance and want, is everyone's responsibility.

Well, you might want to consider how Scrooge acts before he receives his night-time visits and then also how he acts after this life-changing experience. One of the clearest examples that has to do with charity and people supporting one another in society comes when Scrooge is stopped in the street and asked for some money to give to the "Poor and destitute." When Scrooge quizzes the man about the structures that are already in place to help such individuals, the man eventually says that whilst such structures (such as as the work house) did exist, many would rather die than go there or cannot go there. Scrooge's response is rather chilling to say the least:

"If they would rather die," said Scrooge, "they had better do it, and decrease the surplus population."

This is actually a reference to the theories of Thomas Malthus who argued, rather controversially, that if man is not able to offer something useful to society, then he does not have any right or claim to food or life. However, notice how Scrooge certainly experiences a massive transformation towards the end of this story. When he approaches the man that he had previously re-buffed so strongly, Scrooge obviously says he will give a very generous donation, with a "great many back-payments" included in it. The way that Scrooge moves from being a selfish old man to an active participant in society, helping Tiny Tim escape an early grave and other good works, shows the importance that Dickens places on such acts of charity.