Those were initially planned with chrome but I luckily talked them out of it, pointing to the fact that they would not want to be perceived catering to a small archaic bling-bling obsessed minority, but rather do things in style. It was hard work, but worth the effort.
Availability of chrome hardware cannot be the issue, Grabber II, Novoselic RD and Explorer all had chrome three-point bridges and tuners. I think it is actually a conscious design decision to keep Gibson TBird hardware black. It does have its fans, you know.