I believe that the CRI was abit of a suprise for the CAA.
It came with the introduction of JAR and nobody had much clue about it apart from it had appeared in the grand scheme of things without anyone looking at it.
For what it costs it is a particularly powerful rating.
The renewal requiments are far less than the FI rating (and much cheaper)
And you can gain a CRE ontop of that as well for a considerable sum. So you can sign for ratings as well.