Because your life isn’t worth the extra dollar to them.
More accurately, if they added one single extra component like that, they would raise the MSRP by like $500. Because we live in capitalist hell. Therefore, it’s included in higher quality cars, and/or as an optional feature. Like most safety anything, they won’t automatically include it in anything unless they are literally forced to by law. And even then though sometimes not and say they did. And still up charge you for it. Isn’t capitalism fan-fucking-tastic?
They take the worst of the three options. They don’t eat the dollar, they don’t put it in the base model for 500 dollars extra, they lock it behind the big wheels, sporty engine, and wood trim so only the rich people have safety features that aren’t absolutely required by law.