mho it devalues the game. beating the game means less with this feature in place. So what if you have seen the end credits - that proves you got as much skill and problem solving abilites as a potted plant. Its cool for kids, but there's no shaking the kiddy image of Nintendo now. They arent even making games anymore, interactive art maybe? Games have a winner/loser and challenges that have to be overcome for rewards and to advance, this feature puts it on the level of a movie or some sort of leapfrog game.
Did You not read
It is optional