Eric Carmen was on to something. Of all the scary visions and horrible emotions A Christmas Carol describes, there is pretty much none that is quite so overwhelmingly devastating as being all alone. Over and over again we get to check out people who have been geographically or mentally isolated by their life circumstances. In all of these cases, everyone we see struggles as best they can to reverse the isolation and to seek out other humans to hang out with because, you know, that's what humans do. That's what makes Scrooge such a monstrous weirdo; he has isolated himself rather than being forced into that state.
The scenes of people buying the preparations for Christmas celebrations are, if anything, even more important than the scenes of people actually having Christmas parties.
The person Scrooge is most isolated from is actually himself, and the novella is a long journey of the man coming to recognize his own humanity.