In my pure experience, I can always find a Nether Fortress with 500 blocks in all directions from spawn, if not, closer. And all that's really needed to get blaze rods easily is flight which the regular jetpack can do just fine. They are pretty easy to get early game, I could probably get it under an hour, if I strictly went for it.One, not everyone is that good at the game.
Two, not every world has a nether fortress anywhere near where they enter. I've heard of people not finding any within several thousand squares. And the Nether is difficult to both travel and see in, especially if Natura is installed.