By default, when you create a Mac application, it is endowed with certain characteristics. One of those is that your application will remain active even when you close all the open windows. The justification is that you may want to create a new window or open an existing data source, so you need a way to do that once all windows have been closed. However, depending on how your application is intended to work, this can equally be frustrating for users who, when closing the last window, may expect the application to close too.
