They're to let light into the floors below.
As you can see, they have dots on them. This is so that people can see that they really are glass and not gaping holes.
The word is that they're going to be replaced by frosted glass soon, though, even though the building has been open barely a week. It turns out that if you're underneath them and look up, the dots don't really do much to prevent you from getting a glimpse of what lies beneath skirts passing overhead.
I'd have thought that this is the sort of thing that would have been covered in the first "working with glass" lecture at architecture school, but it seems not.