Comment by hnlmorg
Spectators don’t seem to mind it in rally race car driving, downhill skiing, bobsledding, and other timed events where multiple competitors cannot share the track.
Spectators also don’t seem to mind for diving, gymnastics, figure skating, equestrian and other events which are points defined and competitors are also performing sequentially.
Your first list of sports are all single participant because of safety. Every one of those has a significant risk of injury or death that is unavoidable for the sport and nobody wants to die because the competitor next to you makes a mistake. Spectators would absolutely pay to watch it, however (see MMA, boxing, etc).
The second list are not judged by racing against the clock and therefore pointless to compete simultaneously.