the availability of races depends on what the folks at the track want to run. if it's an "official" race that is sanctioned by the powers that be, then there are very specific class requirements. i have found that a lot of tracks have a sort of "agreed on" class requirement list. so there very well may be races for brushless/LiPo setups.

you are correct though, you don't need to run LiPo/BL and if you don't, you'll save a bunch of money.