GO AHEAD, DRINK AND DRIVE ....

Seems to me, that residents of many countries other than the U.S. are quite comfortable leaving a drink that may have been barely touched on the table .... the drink is a relatively minor part of the main activity which is spending time with friends and acquaintances. 

Many Americans, on the other hand, will finish the drink off when they leave, even if they are going to another place and can get another drink there ... the mentality being "don't want to let it go to waste" or "I spent good money on that".

This pattern of thinking is part of the reason behind signs like this ....

http://www.burbia.com/node/4354