I expect a car manufacturer to do extensive real world testing in all possible conditions- heat, traffic, etc. before selling it. A spaceship needs to work perfectly the first time, the actual use is also the only real world test of the prototype. It’s also a much harder problem… cars are much simpler and well understood “mature” tech where we have over a century of real world experience on what type of failures are possible and how to mitigate them.
A mechanical engineer can lose their license if their work results in deaths.
A software engineer can't lose their license because they don't have one.
Perhaps a professional license may improve software development and thus better software in consumer products like cars where bad software design can result in deaths.
I don't think it would need to apply to all SWEs, but would make sense for safety critical things like firmware that runs vehicles, roads, bridges, etc. Certainly the sort of systems that interact with or control other systems already requiring a PE.