Why does the first ghost to visit Scrooge have to be Marley? In the reading, "A Christmas Carol"

Jacob Marley, Scrooge's business partner, has died seven years previous. Inside the office. He says that Scrooge will be visited by three spirits over the next three nights--the first two appearing at one o'clock in the morning and the final spirit arriving at the last stoke of midnight. He rises and backs toward the window, which opens almost magically, leaving a trembling Scrooge white with fear. The ghost gestures to Scrooge to look out the window, and Scrooge complies. He sees a throng of spirits, each bound in chains. They wail about their failure to lead honorable, caring lives and their inability to reach out to others in need as they and Marley disappear into the mist. Scrooge stumbles to his bed and falls instantly asleep.