Because each of these perps were not on their first, second, third, fourth, fifth, or sixth violent offense and were freely out to kill:

https://en.wikipedia.org/wiki/Killing_of_Debrina_Kawam

https://en.wikipedia.org/wiki/Killing_of_Iryna_Zarutska

https://www.cbsnews.com/newyork/news/nypd-men-pushed-subway-...

Many more such cases occur and aren’t widely reported. I’ve personally witnessed a stabbing on a bus

My chances of being stabbed inside my car are much lower