Some people just like to be seen with the cups. It's trendy.
What I'm about to say is the truth:
The reason why laptops are much more popular these past few years isnt because of it's portability. It's because they are a fashion accessory to be shown off at Starbucks.
I never use the office bathroom between 9 and 11am. That's when all the people who have had 2-3 cups of coffee (maybe a cig or two) drop enough rancid shit to kill baby seals without the use of clubs.