What does Banquo feel he owes to Macbeth( even though he doesn't trust him)?

First off I am in 10th grade and I feel Shakespeare is a really easy, but sometimes i find the english confusing so before you decide you aren't so good at it think twicw everyone struggles with shakespeare even he himself. So this question really got me I felt confused, after i had read it about 5 times i realized... oh even though he doesn't trust him Banquo still feels he should and has to show up for the banquet he has been invited to by Macbeth. But why you may ask after what he suspects him of. "Fail not our feast. '' My lord, I will not" (3.1.31-32).