Because you might need to reply to a specific email with all the same people CCd in who wouldn't necessarily be copied in by the bugnumber address. It also inc

Because you might need to reply to a specific email with all the same people CCd in who wouldn't necessarily be copied in by the bugnumber address. It also includes the appropriate message ID to make threading work. And you can quote the necessary bits to put the reply in context. The fact that you need to jump through these hoops to respond so that people will see your reply is another reason why it's a really painful and inefficient workflow.