I believe space is actually a protected industry, and your run of the mill h1b isn't good enough, you need citizenship too - see the ITAR reqs on SpaceX job openings: https://job-boards.greenhouse.io/spacex/jobs/8101417002
That's because SpaceX has military and national security contracts, not because it's space as such.
A policy of the US to attract talented people.
Immigration of talent is historically an American asset. Look bo further than the moon landing itself for an example.
What does that have to do with H1B engineers, who typically end up writing crud apps for banks?.