Defining big obvious functionality is usually easy to get from people. It's all the finer details that people might not know. You might have a feature that's be

Defining big obvious functionality is usually easy to get from people. It's all the finer details that people might not know. You might have a feature that's been relatively untouched for a while, but people still use, so the devs have either left or forgotten from their past "drive-by development".