Games don't come with manuals now, so players have to taken through the controls during the game.
As others have said, just because you personally don't need to be shown, doesn't mean others don't.
Restricting what the user can do and taking them linearly through the different actions makes it easier to design and stops the user from screwing up the flow. Eg., if you could jump from the very start and then part the way through the tutorial you're taught how to jump, that wouldn't make sense.
Saying that, there's no reason why they can't be optional, unless they're tied to the beginning of the actual story/game.
As others have said, just because you personally don't need to be shown, doesn't mean others don't.
Restricting what the user can do and taking them linearly through the different actions makes it easier to design and stops the user from screwing up the flow. Eg., if you could jump from the very start and then part the way through the tutorial you're taught how to jump, that wouldn't make sense.
Saying that, there's no reason why they can't be optional, unless they're tied to the beginning of the actual story/game.