Reversing is illegal as it can result in big accidents. If you race for a bit you will see plenty of stupid accidents caused by people crashing then rejoining the track with little or no care about other cars. Imagine if they had reverse!
Plenty of high end speedys have reverse. All top end SP speedys have the option of forward/brake or forward/brake/reverse with the same settings. Brushless has this advanatge over brushed in the reverse in managed by the software, not the hardware.
If you have reverse save it for practice days with no other traffic on the track.