Why banded armor (lorica segmentata)? Why not breastplates?

[Tarbicus]

Could it also be that it's easier to custom fit to an individual? If the plates were precut (large size) and formed by a large fabrica, then shipped to the location, the leathers could be custom cut to make the seg fit the individual after the appropriate plates were shortened. All you have to do then is rivet it all together at the fort's fabrica. A very efficient means of tailoring, especially for batches of recruits - the segs wouldn't all turn up at once for a whole legion.