The whole truck bed and the height of the vehicle would obstruct basically a tons of stuff, making it a massive blindspot. Lots of accident/collision happened because driver reversed into someone/something.

This sort of door handle, while it's unsafe in certain condition, is lower in priority than those that would cause harm to someone other than the driver. Eliminating blind spot should be in the top priority of automobile maker.

Mandated rear view cameras came from recommendations from a series of particularly tragic coroner's inquests.