Do you raise your pinkie when having your cup of coffee in the morning or eating your sandwich for lunch?
I do.
Involuntarily.
Is there a medical term for this…condition? What’s its purpose? And where did the practice of calling people like us snobs originate?
Lack of a) interest; b) a cogent explanation?
I’d rather think it’s the latter… 
When handling a coffee cup, as opposed to mug, I also do, again also involuntarily.
The custom seems to derive from the fact that all four fingers will not fit into the handle of a cup, so what ought one to do with the weakest, least-necessary-for-holding-the-cup leftover finger.
And insofar as I know it is not a rule of etiquette, but an Urban Legend about the requirements of etiquette. Anyone know better on this?
A place to hang your doughnut while drinking and turning the page of the newspaper all at once?
Oh, yes. Your knee turns the steering wheel …
I like Duckster’s doughnut theory.
On the other hand, I’m a bit disappointed with Polycarp’s summary answer:
I guess I just expected more from this veteran and well-respected poster…