This page in a nutshell: Lack of action by others can mean lack of interest.
Is your complaint not getting support because of a vast conspiracy by the New World Order to build Black silos to block you??
Nobody cares relates to the civil idea that an issue that one person holds special may not engender interest or a feeling of concern in others. If you have been pursuing a complaint for a long time and it has resulted in little or no support, and repeated requests to drop it and move on, then consider the possibility that this is because "nobody cares", rather than there being a vast sinister conspiracy to protect someone you've decided has done something wrong.