How do you know it was for no reason?
Measuring by map size makes no sense. It's the content in the area you have, not the map size. Would you be happy if it was opened up but nothing in it? The game has plenty of content, far more quests than Fallout 3.
I don't think the argument is really that the FONV is devoid of content. I love the detail gone into the game.
It's simply that the map was designed to suggest a great deal MORE area than there actually is. If you like to explore, you're kind of taunted by this giant expanse of nothingness that you can't get to but you KNOW it's there. If they were not planning on doing anything with it, it should not have been included in the viewable map in the Pip Boy.
I will wait to see what they do with the first 1 or 2 DLC packs, but after that, I'm gonna consider the area fair game for modding.
I personally was a little disappointed by the way that the game attempts to make you run a very linear path. I know that's Obsidian's doing to ensure that the story gets presented in a non-glitchy way that makes sense, but it still bugs me that I'm still pretty much ushered along the road to New Vegas by way of Invisible Freaking Walls and mysteriously locked gates. <.<