Because the series started open world. You can go everywhere connected to land from the start. It'll just take longer and you might not make it, once tougher enemies start popping up.
Linear item gating started as early as Zelda 2. You need a hammer to take down the big boulders, a jump spell...
I'm down for open world, just add some good dungeons and ditch the glass weapons. I swear they hired the guy who makes Sir Arthur's armor. (You notice his fabulous heart undies are indestructible, maybe they should make his knight armor out of that.)
Incidentally, how are the dungeons in...