Your nomenclature is a little off, there weren’t 4 groups of any class. Yes, they were split 4 ways (ABCD) but two always ran together, so only 2 groups.
Also, keep in mind the financial impact there would be on the teams if SKUSA cut the classes or number of competitors. Further, while Rotax aren’t SKUSA classes, there are two series, Can-AM and Texas that run SKUSA and Rotax classes together. Let’s not forget all the other world class drivers that were “in town” for the Worlds and it all starts making a lot more sense for their inclusion this year.
As an employee and someone that works closely with the scoring team I would prefer to move away from the split days. But only because of the strain it causes for the girls in scoring with regards to the BIG classes and getting merges, grids and points finished in time. It has grown to a 3 person team and the girls killed it this year! With 5 BIG classes too, the most we’ve ever had).
But the teams, drivers and casino LOVE the split days. Most teams need to employ fewer mechanics and some mechanics can even work for 2 drivers and double their income. And drivers aren’t stuck at the track all day. This means more people potentially have more time to gamble :)