Or simply procrastination. If there's no hard deadline and there are more interesting things to do, keep putting it off until it would be embarrassing to bring it up again. And then never mention it again. Who, after all, is proud of, say, an email kept "unread" for 4 months because you really should get to it, and then quietly toggled to "read" because that's now the prudent thing to do (as opposed to following up on it that late). In that context, it also makes sense not to correct anyone referring to you as "Dr. So-and-so". "No, I don't have a PhD... why not... oh because..." never mind. Just let the sleeping dog lie.