It's a good question, and one that doesn't reflect kindly on many of the serious games out there. The author is especially derisive of training games that mirror the repetitive, mindless nature of the workplace -- games that are "less alluring to people who love games and more alluring to people who don't. Your boss, for example."
The author suggests that developers who want to make learning fun should focus on the fun first and the learning second. We couldn't agree more. We learned more about urban planning from SimCity than we ever learned about arithmetic from Math Blaster -- mainly because we kept playing SimCity long after Math Blaster got donated to the secondhand store. In other words: you can lead a player to an educational game, but you can't make them play. They have to want to do that.