The word obligation means to be bound by a sense of social or legal duty. Under this definition, Maycomb's obligations extend only as far as its public consciousness will allow. For example, the Ewell kids are not expected to attend school all year long because forcing them to go would create more unrest and problems for everyone concerned if they were. So, Maycomb has a legal duty to offer education to them, but because of the feared consequences, they don't force the kids to go.
Maycomb must also offer a fair trial for Tom Robinson, legally. There must be twelve men on the jury, both sides of the case must be heard, and Tom must have an attorney. These things, however slighted because the jury is all white and racist men, are provided to satisfy the minimum requirements of law. But the community does not feel obligated to give Tom's wife Helen a job while her husband is in jail for over a year. In fact, she's shunned socially and economically while her husband Tom is given a "fair" trial. Thus, Maycomb feels obliged only to make things look fair legally, but socially, black people like Helen suffer.
Another example of how Maycomb shows their feelings of duty is if one compares how Mrs. Dubose is treated compared to Dolphus Raymond. Mrs. Dubose is allowed to sit on her porch with a gun under her skirts and yell racist and mean things at children who pass by. On the other hand, Dolphus Raymond is shunned for having interracial children. Legally, the people of Maycomb can't run a white man out of town, but socially, they can talk behind his back and treat his children with scorn.
One of the best examples that shows where the community's sense of duty really lies is in chapter 26 when Miss Gates talks to her third grade class about Hitler's treatment of Jews; but, she doesn't make the connection for her students between the persecution of the Jews and the persecution felt by the black community right there at home in Alabama. Scout articulates what happened in class perfectly by the following:
"Well, coming out of the courthouse that night Miss Gates. . . was talking to Miss Stephanie Crawford. . . I heard her say it's time somebody taught 'em a lesson, they were gettin' way above themselves, an the next thing they think they can do is marry us. Jem how can you hate Hitler so bad an' then turn around and be ugly about folks right at home--" (247).
Scout nails it! Maycomb only feels obligated to assist those who share their views, and if it is required by law, they will offer the bare minimum to uphold the law without drawing attention from the federal government. They take care of their own who are white, but they don't feel like they should help the black community--only to keep the black community in their place as servants in the community and not as leaders.
One final example of Maycomb feeling obligated to help only their own white people is exemplified by Sheriff Tate covering up Boo Radleys heroism in chapter 30. He explains as follows:
"Mr. Finch, ,taking the one man who's done you and this town a great service an' draggin' him with his shy ways into the limelight--to me, that's a sin. It's a sin and I'm not abut to have it on my head. If it was any other man it'd be different. But not this man, Mr. Finch" (276).
Sheriff Tate didn't help Tom Robinson by covering up his case, but he does help Boo Radley, who is white. It's the right thing to do for Boo, but Tom was an innocent cripple with a wife and three children to support. But since Tom was black, Tate didn't feel obligated to help him. Individuals such as Miss Gates and Sheriff Tate represent many of the people in Maycomb and their attitudes. There are only a few who are like Atticus, such as Link Deas and Miss Maudie, who don't see color lines. But in a lot of ways, it's the color lines that make the difference between whom Maycomb feels obligated to defend or to throw to the wolves.