Ph.D. speak

Ph.D holders have a secret handbook, I'm convinced. In it, there must be a chapter on how to sign off on emails because nearly every professor and friend I know with a Ph.D signs off with the word "Best." It doesn't matter their age, how long they've known me, how old they are, or how long they've had a doctorate--they all sign off the same way.  Example:


Cara,


Thanks for leaving the signed form on my desk. I'll send it on to the English office and email you with what I find out.


Best,


Dr. Smith

To be clear, there's nothing wrong with signing "best." It general communicates well wishes to the receiver, but it's also curiously vague. Best what? Are the missing words before "best," as in (I'm the) best or (you're the) best, or is it after, as in (I wish you the) best? Is it just me or is this a national phenomenon, part of a secret code of conduct for professors? And am I allowed to use that word when I sign emails even though I'm not a professor? If I ever have the letters Ph.D. after my name, I think I'll sign off differently just to buck the system...since I'm so rebellious and all. Maybe something professional like "Your awesome professor" or "So glad I'm not in your shoes."