I know it seems odd, but my guess is that it condenses 6 hours of qualifying into a nice 1 hour prime time TV show. Surprise, Surprise.
And recovery
is a problem. If you put it in the gravel, or worse, its game over, just like F1. At least the prequalifying is at the end of Wednesdays sessions, but its in the dark.
We then have the practical issues for spectators, as we usually bbq about 9:00, and are in bed by 11:00