You do though. Without legislations, cars wouldn’t have safety features by default like crumple zones, airbags etc. Without legislations, companies could do whatever they want to pad their bottom line. You need laws to define what is and isn’t acceptable, especially when it comes to safety.
Before we started legislating car safety, more often, if you got in a crash at speed, you would be either dead or seriously injured. It was not uncommon for a front-end collision to shove the entire steering column into, in some cases THROUGH, people’s ribcages because there was no shock absorption. “Defensive driving” - avoiding a collision at all costs - was taught mostly because of this sort of problem.
I’ll speak to the effectively of modern safety engineering myself - I was involved in two serious accidents within the past two years that, were I in a vehicle without safety features, would’ve left me dead or crippled for life. One, my Jeep spun out on a patch of wet road and got slammed by two other vehicles in a pinball situation - airbags deployed and I was left with some soreness and a thoroughly-wrecked vehicle. The other, my work van got T-boned by a semi truck at speed while crossing an intersection - once again, the airbags deployed, the seatbelt locked me in place, and the fact that the rear of the vehicle was designed to squish in on itself saved me from, at the very least, a severe case of whiplash, and more than likely some severe head injuries.
