won't happen in a commercially built vehicle.

Climb in through the window, since the whole cabin is a roll cage?
All drivers wearing a flame retardant suit and a HANS device?

The roll cage would be too expensive, I'm sure. I can picture the advertisements. "Hi, we have the safest sedan on the market? But it only holds 2, and maybe a little bit of room in the back because the whole thing's a roll cage. You have to enter by the window, and the base model is $85,000 without any luxury appointments....but if you crash into something and flip 5 times, you won't die"

As for the other items, back before bullet proof vests became much lighter, cops didn't want to wear them due to comfort issues. Same with soldiers not wanting to keep that helmet on. Balancing the very small chance they NEED that protection vs. the pain of using it all the time. No way someone decides to wear a fire suit and use HANS for their morning commute.

But, yes, a lot of safety features, and a lot of other improvements have come out of racing. "How do we make the car lighter, more powerful and better mileage, yet still safer" have come from racing.