Public Interest Groups promote collective good rather than selective good. They aim to help groups other than their own members. Public interest groups promote collective cause. A group fighting against child labour on bonded labour offers an example of it.
Public interest group always fight for those rights which ate neglected by the government. Thus they have useful role of counterring undue influence and reminding the government of the needs and concern of ordinary citizen.
So, it can be concluded that given value to public interest group is beneficial for the working of the democratic form of government.