One aspect that I don't see mentioned yet is the change from academia as an upper-middle-class middle-aged white male club to a broader, more diverse group of people (that still needs to be more diverse). Clubs have in-jokes, secret handshakes, common interests aside from their common profession. Professional groups don't. 

When you could assume that most people who would look at your title had a similar background to you, you could be pretty confident your clever little pun would register in the context you meant. Today, hopefully, that's not the case.