Historically, I think that "regional" and "divisional" championship events came first (with the latter qualifying drivers to the national championships), and the concept of "Regional" and "National" CLASSES came later.

Really, the distinction applies only to IT and those region-specific classes. I can speak with authority on the common discussion about IT when it was conceived as a national-rules, regional-only category, since I was around then. The thinking was that this policy and the "no guarantee of competitivenes" clause, that kept the category out of the performance adjustment game, would preserve IT as a low-pressure, low-cost, entry stepping stone to "bigger, better" classes.

Problem is, IT makes more sense than most of those other options, so it has grown beyond them in terms of participation.

K