Why does Grandpa leave on Saturday night in Chapter 10 or 9?

From the text:

Twice since I came to Greenwood, he’d left at night for Council meetings and came back late, long after I was asleep. I figured it was boring political stuff he was working at, probably had something to do with battling desegregation and all that. Seeing him so involved reminded me of Dad: all worked up and smack in the middle of some issue.

Later that evening some men picked Grampa up for another Council meeting.