BCC on email is very useful for stopping email harvesters. In fact only use BCC when > 1 recipient then when the receivers get your email the list of email addresses you sent it to will not appear and as such cannot be harvested. The original usage was to copy people in in such a way that they do not know who also received the memo (now email)
our company usually uses "bcc" for information emails that go to the whole company. sometimes they forget and then you get an email addressed to close on 500 recipients, followed by umpteen "reply to alls" as the company jokers start firing sarcastic comments, and more umpteen "reply to alls" telling users not to "reply to all"......