As far as sidestepping your question (which I did not, but my answer may have been too subtle), the reason why I (at the least) include some humor is indeed to keep it interesting to people playing the mod/game, where they might keep learning more and get more interested in it as a whole. In a classroom I know some students don't need any motivation, but they sit in a room with other people might greatly benefit from a little joviality in the course ("benefit" as it keeps them looking at the material (playing the mod) a little longer or with a little more interest than they might otherwise). You'd really not like me in a class - I usually include a New Yorker cartoon dealing with some aspect of mythology on every myth quiz. And I always have introductory latin classes read a bit of adapted Plautus each semester for fun.