Why does the spirit show Scrooge people stealing from him after he dies?

The Ghost of Christmas Yet to Come provides Scrooge with a frightening glimpse of the future. He shows him how people behave towards a horrible old miser who has only just passed away. Certainly no one will attend the man's funeral unless there is a decent spread available. Most worrying of all, the ghost shows Scrooge a number of people stealing from the very same individual and passing on his stolen goods to a fence. Of course the dead man in question is Scrooge, as he eventually comes to realize.
Two of the people involved in the theft work as domestics for Scrooge. Their theft from him is rather symbolic. It is fair to say that Scrooge treats his domestic servants much the same way as he treats Bob Cratchit: very badly indeed. We can be sure that he pays them pretty abysmal wages for all the hard work that they do for him. Their theft of his property is a kind of payback for all the years of mistreatment they've suffered at his hands. By chronically underpaying them for so long, Scrooge was effectively stealing from his employees. Now they see themselves as simply returning the favor.