H1-B visas eventually expire. I think it’s technically a guest worker visa, so the expectation is that the visa holder will go back to their home country after working in the US a few years.
The statutory protection for H1Bs is thin. In 1990, Congress excluded H1B from the requirement applicable to other non-immigrants that they retain a foreign residence, and from the rebuttal presumption that someone who applies for a green card has immigrant intent. That’s it. The common operation of H1B as being an immigrant-intent visa is mostly a matter of administrative grace.
The 1965 immigration act was sold to americans on the idea that it was simply ending country-origin discrimination, and wouldn’t increase immigration or change america’s demographics: https://www.nytimes.com/2024/10/29/podcasts/the-daily/electi....
So Congress can take advantage of the fact that a lot of people are okay with the status quo, but can’t affirmatively enact legislation that would be seen as creating a new pathway for permanent immigration. So the current system was built on a series of small measures that could fly under the radar. Eliminating the rebuttable presumption of immigrant intent in subsection blah blah blah doesn’t sound like it’s going to create a new pathway for permanent immigrants.
I was on H-1B at a university where researcher appointments were nominally from July of year N to June of year N+2. But if you didn't start in July, your second appointment might be only 1 year, for some bureaucratic reasons. And you had to renew the H-1B for each appointment. I had five H-1Bs in total over ~7 years.