That becomes painfully clear when your boss reaches out directly to the candidate for a follow up interview because she thinks this was your intent in Cc'ing her. So why do we add people to the Cc and Bcc fields so often? Perhaps it's because we think it minimizes our own liability in a given or maybe working as a team mandates it.
In either case, without context, people added email list to an email will always have some degree of relationship disparity and are at risk of being unaware of why they've been added or what's expected of them. A good rule of thumb is to give a moment's thought to everyone you've added to the email and ask yourself, what is this person's relationship to me and what information do they have (or not have) that will allow them to respond accordingly.
Structure Matters I've given a few presentations about email effectiveness and I like to point out the 50/50 rule above because it tends to makes people think. One day, a manager from one of the large email vendors mentioned to me that while it was true, people do tend to misinterpret tone, some people are simply poor communicators. In other words, some of us simply can't string the words together to save our lives.