It's to do with the ergonomics of comfortable eye placement...
Really?
Because I disagree. I'm sure other games split up their HUD too, but the one that comes to mind right away, because I was playing it recently, is Titan Quest. It's got the health/mana bar up in the top left, just like Brink, and it has your skill bar in the bottom of the screen, mostly focused on the left side. So a bit like the 'ammo wheel' in Brink. I found this setup to be anything but relaxing, and many others have complained that the top left is
not a good place for the health bar.
I don't think it will be too big of a deal, but I really do hope it's customizable, as I would prefer it down nearer the Supply display thing. I think splitter up the HUD elements too much isn't the best idea, really. As I said, though, I doubt it will be too big of a deal either way.