Well what if I want to be invisible to say four people? I don't have anything to say to my other contacts, but maybe they have something to say to me! I'd have to message them and be like "k I am on right now, but invisible. Okay I'm logging off now, I'm not just invisible." every time. It's awkward and tedious! Plus it just looks really pretentious when you talk to someone when you're invisible. Like, "who the smurf do you think you are? Are you so important that you have to be ninja all the time?"