how do banquo and macbeth differ their responses to the witches prophecies?

In Act I scene iii when the witches give their prophesies to Banquo and Macbeth, we see Banquo is more concerned about the witches' motives than Macbeth is. Banquo considers that the reasons for the witches offering such fantastic futures to the men may not be honourable-

And oftentimes, to win us to our harm,

The instruments of darkness tell us truths,

Win us with honest trifles, to betray's

In deepest consequence.

Macbeth simply focuses on how he can assist the predictions coming true, not the motivation of the witches.