I'm a little confused.

If you're sending a Private Message, shouldn't it be kept private?

Lets say I have the same message to send to a variety of people. If the receipient thought that I was sending the same message to multiple people, it would lose some of the specialness. It also saves me time sending the same message over and over again to multiple receipients just to personalize it by adding their name.

Sort of the same as BCC.