Why did the ghosts have such misery in the Christmas carol?

Answer 1

They didn't all have misery. The first showed Scrooge both good and bad points in his own past thus showing him some of the reasons his mind set was as it was, the Ghost of Christmas Present was a giant of a man with a huge bellowing laugh and spread Christmas Cheer as he went along. However, he became more serious when speaking of the potential death of Tiny Tim and reminding Scrooge of his own words, "Are there no work houses, are there no prisons?" and also when showing him the children representing Want and Ignorance both of which were of mans own making

Answer 2

The ghosts in "A Christmas Carol" were burdened with misery because they were trapped in a cycle of regret and sorrow from their past actions. Their purpose was to show Scrooge the consequences of his own choices and the impact they had on others, in hopes of helping him change his ways before it was too late.