Question

why did the ghost want people to stop playing the ouija board

Answer 1

The ghosts had asked for a promise from Hallock that they would not be using the Ouija Board.  This was so because they were on a strike. They hated being called upon every time somebody needed to write a ghost story or wanted to play on an Ouija Board.  This was the reason they were agonised and did not want the guests to play on the board.