I guess the term "common" is going to be problematic because it's subjective.
Lets just say I've personally observed maybe a half dozen people drinking from regular mugs like that over the years - and it's not like I spend my life trying to see what mugs people are using. I simply meant that it's not really news worthy.
It's a stupid idea. I've been in cars where the driver does it every morning on the way to work. To the surprise of no one coffee goes all over the car most days.