Because Shakespeare apparently though the ghost of Banquo would be more effective in the drama.
Macbeth sees the ghost of the recently murdered Banquo.
The ghost of Banquo.
Macbeth kills Banquo in the play and then Banquo's ghost haunts Macbeth.
In both cases, the ghost that appears in Macbeth is summoned by the guilt and inner turmoil of Macbeth himself. The ghost of Banquo is a manifestation of Macbeth's guilt over his role in Banquo's murder, while the ghost of Lady Macbeth represents his guilt over her death and his descent into madness.
Macbeth kills Banquo in the play and then Banquo's ghost haunts Macbeth.
The ghost of Banquo appears to Macbeth one time during the banquet scene in Shakespeare's play "Macbeth."
Banquo's ghost. But let's be fair; Macbeth told him to "fail not our feast", and Banquo didn't, even though he was dead.
Macbeth
Macbeth sees the ghost of the recently murdered Banquo.
Macduff takes Macbeth's place at the banquet in the play "Macbeth." Macbeth had planned to sit at the head of the table but gets unsettled by Banquo's ghost, so Macduff takes his place instead.
In Shakespeare's play "Macbeth," the ghost that haunts Macbeth is the ghost of Banquo, a former friend whom Macbeth has murdered in order to secure his position as king. The ghost appears during a banquet hosted by Macbeth and is only visible to him, causing Macbeth to react with guilt and terror.
Lady Macbeth was also missing from the banquet table in the scene from Shakespeare's "Macbeth" where Banquo's ghost appears. Lady Macbeth excuses herself from the table, fainting in response to Macbeth's behavior and the appearance of Banquo's ghost.