The History of crash-test dummies is one of Sheer Deathworlder Thinking. Instead of doing the sane thing and wait, till the technology is safe enough, they relied in the past on test with crash-test dummies.
Fun fact: Aliens did not know, that the First Dummies were actually other Humans. -- Anon Guest
There's a crucial difference between Havenworlders, Deathworlders, and what one might consider normal cogniscents. That particular difference is in how they approach the relative safety of technology. For most cogniscents, new technology is treated as a curiosity until such time as it has been thoroughly tested for all plausible hazards, and then only employed with all due caution. Havenworlders go overboard on all possible safety measures before going near new technology, exhausting every single thing they could worry about until it is fretted into never having a single thing to cause harm.
Deathworlders dive headlong into new technology, often before it is tested at all, and find out about all potential dangers through 20/20 hindsight. Humans, especially, did this a lot. They took the starter knowledge that radiation could treat and eliminate some cancers, and expanded it into a health treatment to eliminate all cancers for more than a decade before discovering... whoops. Radiation can also cause cancers, too.
They put motors on carriages formerly drawn by horses, and then make them go as fast as possible. Then they wait half a century or more before figuring out that -perhaps- the bodies within should be restrained for security in the event of an unexpected collision. How do they test this? In the most logical way that Deathworlders are capable of. By using the bodies of their deceased. It just gets worse from there.