I don't presume anything. I'm just pointing out that the article does not answer it's own question.
I repeat: what leads you to presume this is something employees enjoy? I mean, is it conceivable to you that any random person prefers to be forced by HR to attend an event on their own personal time instead of spending it with their loved ones, or even doing something they love?
Just pointing out that for those people who are passionate about pizza parties and whether employees like them or not, the article is not helpful.