A history lesson: The developement of modern day R/C competion grew out of Southern California. Associated Electronics was born there, Team Losi, Proline and the list goes on. One day some one had the idea to run oval pan cars on a bycicle velodrome in Encino Ca. These where special events which Dan the "Bananna Man" promoted called "Thunderdrome". To make these races even more interesting they decided to hold an "Insane Speed Run" for 1/10 th scale R/C cars. The rules where much the same as RCCA's except you had 2 minutes to make your fastest complete lap.
The aging of the Encino Track made it difficult to keep the cars on the ground. Then with the opening of the 7/11 Velodrome for the Olympics in Domingus Ca. the cars started flirting with 100mph on a slippery 32 deg. banked concrete oval.
Then there was the demise of the Domingus track to make room for a Soccer Stadium which left nowhere to hold the Insane Run. It seems Cliff and Associated really wanted to top the 100 mph mark and arranged to run at the newly constructed Irwindale 1/2 mile.
So the idea of R/C speed runs on oval is deeply ingrained in the minds of the folks who started it all.