Strong Towns is attempting to change that with the "Crash Analysis Studio":
https://www.strongtowns.org/crash-studioI can think of many reasons it's difficult, though:
* The fact that accident investigations are designed to figure out which driver was at fault, for insurance purposes
* The fact that road designers are shielded from liability (good, right?), but only if they can show they followed the standard design handbooks, which not only fail to prioritize safety over traffic flow but also don't require or even contemplate performing a thorough case-by-case investigation into how to prevent a certain type of accident from happening again. (Crash Analysis Studio tries to demonstrate how to do this.)
* The sheer scale of the changes to roads that would be needed. In the States, access of hundreds of thousands of businesses and probably millions of homes depend on roads that are supposed to get people from A to B fast but also have lots of access points for businesses on them, which is like just like mixing taxiing and holding with takeoff and landing, but without the air traffic controllers. And don't get me started about unprotected lefts across multiple lanes of traffic.
* The lack of buy-in from the citizenry for enforcing professional-like standards on drivers. Despite the blameless culture that helps identify flaws in the system, air traffic controllers, pilots, maintenance crews, train engineers, etc also know that their job depends on making a sincere effort to follow the rules that are written, and in most cases their professional identity is tied up with following the rules. (I've heard that to be a pilot you really have to be comfortable with doing what you're told, all day long.) There's really no obvious way to get the masses of drivers to think and feel that way about their driving, and of course we can't just sanction our way to compliance because people need their licenses to go about their lives. And of course usually there is no reasonably alternative to driving yourself where you need to go.