Talk about a rude awakening!
And yes, I do drink wine sometimes (at night!) out of a coffee mug for utilitarian reasons:
Low center of gravity to prevent tippage (this problem seems more prevalent as more wine is ingested);
a handle to prevent warming from body-heat;
the discretion factor (heh - I'm low profile);
much lower fragility factor when knocked off of table (again, more common as more wine flows, for some odd reason);
and they're easier to clean and/or put in dishwasher.
I'm sure Julia Child is spinning in her grave.