TL,DR: Who the hell knows. No idea. Why can't we go to the Plaguelands or Mars? Where I'm sure the Cabal would be interested in SIVA. People would bitch about it being recycled content, but it would be a valid reason for it to be around. That's unless the Cabal decided to slam The Exclusion Zone with Photos. I can see that being a reason for the Rasputin DLC. Him telling us Cabal are trying to get their hands on SIVA. Why not? We got the annoying ass Taken. Why not throw SIVA-infused Cabal at us? And we see Rasputins Frames that he used against the Iron Lords that haven't been seen before nor since then. Which I have a feeling are Proto-Exos. More likely them just being giant RedJack Frames, since that's all the bosses are right?...... Just bigger versions of existing enemies. We got a giant Hobgoblin, a giant Vandal, a giant Shrieker, giant Cabal, giant Minos, giant Servitors, giant Captains, a giant Harpy, giant Ogres, giant Knights, and giant Hydras..........why not throw in some giant frkn Thralls, Dregs, and Goblins. Because why not make unique looking bosses when we can just make giant versions of the current, change a few details, and boom a totally "new" enemy is born. Guess this turned more into a mini-rant as I typed...... eh screw it. Edit: Giant Shanks too. Edit 2: Expect a giant Psion soon too I guess.

The word "Temple" could offend people, gotta play it safe to avoid the Social Justice Peacock's.

Because the Iron Lords were having trouble with the copy/paste function. They couldn't bring it into D2 without actual effort so they passed. Should be accessible in DLC later though.

They're gonna rerelease it in a future DLC.

You haven't paid for the reskinned version yet.

They could of just fallen back to the temple

It will open up for Ib.

Because hard drive space

Nothing is explained, it is kind of lazy.

because its prepared to be rehashed in one of the next DLCs

Or old Russia Or the moon Or mercury, Venus dreadnaught etc

That lazy BITCH Saladin didn’t pay his -blam!-ing rent, so got all us mutha sucka’s evicted!

As many comments have already said before me, it will be rehashed and brought out with "new" DLC content, most likely the 3rd as the season pass gives you 1 and 2 and Bungie are sucking all the money out of the community and giving us recycled content. So if you want to go there so badly, you might as well play D1 again cos there probs gonna charge us around $/£30 for the DLC which I can almostguarentee will not feature a raid cos Bungie wil be too busy counting all the money being thrown at them by youtubers just so they can have a source of income. In reality, they are giving Bungie more incentive to give less of a -blam- about the game and that will mean the content will rapidly decline until we are left with bare bones, by which point everybody will have moved on by having a social life or playing games that are actually enjoyable.

Becuase your not playing D1.

The same reason you can't go to the moon, old russia, mars, venus, the dreadnaught, the reef, etc. Those areas were a part of the D1 map and storyline, and not a part of the D2 storyline. It's the same reason you can't go to the imperial city in skyrim, to Eden prime in mass effect 2, to denerim in Dragon age 2, to Rome in assasins creed 3, etc. The area was not created for the sequel.