Katy Perry's Photo of John Mayer in a Santa Suit Might Cause Post-Christmas Night-Mayers

Katy Perry tweeted John Mayer in a Santa suit and blarg. I don't get that dude, how does he consistently score with the ladies? There are about 3.5 billion men on Earth that Katy Perry could date (yes, I'm counting olds and babies, both arguably superior choices) and yet...