Not sure why myself. After briefly checking on google. It appears Ghost and Spirit could be used in the same manner. Accept that sometimes Spirit could be used to identify a literal human being. For example 1 John 4:1 Beloved, do not believe every spirit, but test the spirits to see whether they are from God, for many false prophets have gone out into the world.
Here the word spirit can refer to a human. So, truth be told I am glad the translators used Ghost, so there is no confusion. Actually now that I think about it, when I watch a theological debate between a Christian vs Muslim, sometimes the Islam believer states Jesus was referring a person there last prophet as a the comforter. And states that's why spirit terminology is used to reference it being a human being. But this logic falls completely flat since they used the term HOLY GHOST, for it as well. Scripture cannot be broken!