I can't give you a link to this because it has been a long time since I read it, but I've seen an article that might explain this. Apparently bronze age Mesopotamian homes were built to create increasing levels of privacy; your most public room, where you'd entertain guests, goes nearest the entrance to the house. Your second most public one might be your pantry and kitchen, which you might use to entertain guests but guests are unlikely to spend a lot of time in, so the only way to access it is via the first room. Then you'd have your private space, like your bedroom, and the only way to get to that is via the pantry.

Like I said I'm working off of hazy memory here, and Nebuchadnezzar is a fair few centuries later than the end of the period that the article was discussing, but I think I can see what looks like that idea of layers of privacy in the image.

Those are likely suites of rooms. You can kind of see the partitions of larger areas before it becomes maze like.

As a palace, accommodations for residents and guests would need to account for entire family size, as well as potential retinue.

I'm not am expert, but it seems that along with the walls thickness, it was one of the methods to keep the heat out and staying cool inside.

If you take a closer look, they are actually quite spacious

Privacy and to confuse invaders. Also, to maintain a solid structure that can hold up the roof. They have to build a structure system for the roof, no matter what. They're making the best of it.

It was a brothel.