Unlike mugs, they don't have a handle and are uncomfortable to hold.
Washing your mug though is a pain in the ass too.. a real time waster.
What can someone like me do, who hates coffee cups AND the environment?
The answer: Disposable coffee cup mug.
Behold!

The mug-cup. I call it the "mup"!
All the advantages of a proper mug, without the hassle of cleaning it. It also says a big "fuck you" to the environment. It says "yes, I have a mug, but I choose to use a disposable cup nevertheless. What did the environment ever do for me??"