Something in open-world games that just got too mainstream

So I recently completed Arkham Asylum, It's a great game and all but one thing pissed me off pretty badly. The were too many god damn secrets/riddles scattered all over the map. A very cheap way to keep the player occupied for the game longer if you ask me. Too many games feature these collectible items and such that takes same amount of time to gather as completing the storyline missions. I don't mind side missions though.

/end rant