I can see you point but in reality most clubs/race organizations, if not all, have specific rules about stopping (or not stopping) on the track when the track is hot.
A rider that stopped for that rider may cause another accident simply by slowing dramatically and/or try to cut across the track when everyone behind might still be at track pace. Besides, another rider stopping with the intent to help that downed rider gains him nothing as the rider stopping for him is not a paramedic nor have the gear to deal with him and in doing so only delay the real paramedics from helping him.
Paramedics can’t be deployed when the track is still hot, and only until all able riders are off the track. Especially in a lot of cases the shortest distance to the down rider could be going in the wrong direction and/or cutting through different sections of the track.
The best way to help him is obey the flags and do what you are suppose to do according to the type of flags being signaled.