They might be using it because of the study about font legibility and learning retention that was all over the news last year:
http://seedmagazine.com/content/article/the_revenge_of_comic...
http://slog.thestranger.com/slog/archives/2011/01/13/new-stu...
Kathy Sierra and Burt Bates also used these types of fonts in their "Head First" series for O'reilly. I have never gotten into those books, but many people love them.