"There'll be scary ghost stories and tales of the glories of Christmases long, long ago." Was telling scary stories really a tradition at Christmastime? If so, why did this tradition fall out of practice?

This one came up exactly a year ago. I answered it then, and you might like to check that answer out while you wait for any other replies. But the tl;dr is: [a] Yes. Because Charles Dickens; and [b] depends where you are. It is still the custom in Britain, where Hallowe'en is not quite the big deal it is in the US.