The genesis of Improved Touring was as a spur of timed-out Showroom Stock, back in the days when Showroom Stock was "showroom stock". That included stock suspension, stock wheels, stock brake pads, stock seats, stock steering wheels, stock pretty-much-everything. About the only thing we could change was tires, add the bolt-in-only cage, harnesses, go racing. Cars were only eligible in the category for 7 years.
Improved Touring pulled from that whole restriction a series of limited modifications, mostly limited to common bolt-on street upgrades. And in fact, the original regs required the cars to still be street-drivable.
As such, IT is, and for the foreseeable future will be, an intentionally-restrictive category.