Same history lesson I've preached many times in the past: We have Nationals classes that are eligible for the Runoffs. We allow regions to create any other classes that they feel fit their local needs.

Improved Touring was an idea that hit various regions in the early 80s and took off, and other regions picked it up. Because there were varying regs in varying regions, SCCA (Englewood CO at the time) agreed to publish a separate book* for IT with a nationally-consistent set of regs, all so that competitors could travel intra-region and not worry about compliance differences, but with the caveat that this was just a convenience and the class was never intended to be considered for participation in the Nationals program.

Time moved on, all nationally-compiled regs were combined in a single book, including IT, and everybody began to wonder why IT couldn't play at the Runoffs.

IT exists in the same plane as Super Production, ASR, SSM, SMT, ITE, ITEZ, ad nausea: regional-only classes. By virtue of historical evolution it just so happens it has a nationally-consistent ruleset (Butch tells me there's others in there, but nothing to the extent of IT).

GA

* The GCR used to be one book, and each category had its own physical book. You had to purchase each separately, only scrutineers got "the bible" with all in one binding...