The reality is, it's a financial decision. SCCA does not allow OW and SR on track with larger production cars and it is not financially feasible to dedicate two or more hours of track time and add an additional run group for a small number of cars.
The last SCCA TT I participated in had a total of only 27 entrants spread over 3 run groups and that was at a track owned by the sponsoring region.
The only way I see a change in SCCA's TTN decision would be a fairly large number of OW and SR participants (30 plus), but that would be reducing available track time to the other groups. I don't see this decision changing unless interest fades or participation does not meet expectations.
For now, I will continue to Hill Climb and run under the old rule set.