Watts has experienced a general surge in the past few years or so-- I'd attribute it to the growing number of Youtube videos featuring audio of his lectures. The 'What if Money Were no Object' video in particular was passed around a lot in art communities and college campuses about two years ago. Trey Parker and Matt Stone animated some of his lectures, adding to the surge as well. Also, the band The Books prominently features Alan Watts samples in their music too, which is how I was introduced.

Perhaps he was included in 'Her' because he has become popular recently.