Why were jem and scout disappointed with atticus

Scout was disappointed that Atticus wasn't going to attend the Halloween pageant.

When Halloween came, I assumed that the whole family would be present to watch me perform, but I was disappointed. Atticus said as tactfully as he could that he just didn’t think he could stand a pageant tonight, he was all in.

During the trial, Scout shares that it seemed everyone was waiting for a climax.... a fight of some kind. If so, her father had disappointed everyone by being his usual, amiable self.

So far, things were utterly dull: nobody had thundered, there were no arguments between opposing counsel, there was no drama; a grave disappointment to all present, it seemed. Atticus was proceeding amiably, as if he were involved in a title dispute.