"I work out and stay healthy."

You are aware that this is not a 100% plan for staying healthy ?

Unfortunately, a fire in one person’s yard is not likely to stay just in their yard. Even if you feel like the people who are responsible should burn to death if they don’t have their own private fire service, unfortunately, their neighbors and possibly the entire community are likely to suffer if the fire is not extinguished immediately.

So in this example it’s your fault you were walking down the street and because you work out being hit by a car won’t hurt you?

Fault is a loaded word, and is inapplicable in this context. The burden of the cost is borne by the party that society that chooses using whatever framework exists. Maybe it was "mob justice" a thousand years ago. Today, maybe its in the form of a lawsuit. Maybe its a social safety net that pays for your medical expenses.