This must be a mistake. Either that, or some sociopath at the mug factory (that's a place, right?) decided to place the handle on the inside to trick people into scalding the ever-loving hell out of their knuckles. Either way, maybe grab a Styrofoam cup instead.
This seems cute until you picture them in use at dinner. Really picture it, specifically with lasagna. The insane contortions of the fingers and the sloppy mess it makes. If you'll excuse me, I'm going to never stop throwing up, now.
Some criminals are actually quite considerate. It's hard explaining to a sketch artist what your assailant looked like when you're in a state of shock. So it's nice to see this pre-meditating perp going out of his way to leave behind a more accurate depiction.