The main reason is that it wasn't immediately apparent to me how the shield window worked when I put in the code, but I figured it probably wasn't something that had to be there, so I left it like that. Balance was one thing that seemed to justify it.
You basically get more control over an already powerful armor set, and more control = more power. So f. ex. by it being visible, you get to pull back / hide every time you see that it's low, reducing risk of damage. I might look into it again though, because it's not a huge thing.