I agree that just because it's obvious doesn't mean it's not valuable, but my position is that it does not deserve the various government-granted legal protections of a patent. If it is obvious then it is something that you run into, not something that you create. By all means exploit your first-mover advantage as much as you can (be it a genre, a market, or a technique), but don't ask the government to grant you a time-limited monopoly. Just because it didn't exist for centuries doesn't mean it took centuries to create.

(note: "obvious", "straightforward" and "easy to understand" have various degrees of subjectivity attached so it's never easy to argument in these terms)