If people didn't get killed racing, pro racing wouldn't exist, it wouldn't carry the ratings. Death fascinates us and we want to see it happen in a spectacular form. NASCAR is the modern Circus Maximus. We want to see people compete to the death. We don't like to admit it, but it's the truth.
I don't fully agree with this. I think there certainly is a fascination with watching an event where there is an element of danger for the participants, if nothing else than to wonder how far we would push our own risk tolerance limits like the drivers do.
Some forms of racing do have a high chance of a sudden and brutal outcome - anyone who's seen a top fuel dragster or funny car slam into a berm or other structure and disintegrate knows that. Other forms are more subtle - NASCAR features a lot of accidents, but rarely driver fatalities. Maybe Earnhardt was the last driver fatality, 2001, in the top series?
I used to follow F1, and sometimes still do, it has a very deep safety culture, now, but it came at heavy cost. Like other forms of racing the cars, teams, and drivers are pushed to the limits of control and sometimes do exceed them. But no one dies (I think a course marshal or spectator has been killed recently, but no driver fatality since 1994).
NASCAR is different, though. Bumping, rubbing, spinning someone, and other full-contact racing is a part of it and that's something I don't see anywhere else.
F1 was having so many driver fatalities it was actually in a state where the whole thing might fold, so they went all in on safety (as much as you can do, and still race). If NASCAR were to lose a driver every month or two (like F1 did for a while), I think their ratings would drop. People want to see the risk and danger, but I think the fight-so-the-death aspect is a little over the top for most spectators.
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I don't think people go to hockey games to watch the fights, either.