H1B's are immigrant visas, they terminate in greencards after one renewal. The only problem is that a few countries have long lines (India, China, Philippines) on how many greencards can be granted this way per year. That should be done away with.
No, H-1B visas are explicitly nonimmigrant visas for temporary workers. [1]
> They terminate in greencards after one renewal
No, they don't. You can apply for a GC, but there's nothing automatic about the process, and the GC is not guaranteed to be approved either.
[1] https://www.uscis.gov/working-united-states/temporary-worker...
The greencard process is a multi step, often many year process. If you are from a country with per country limits you can be approved for a green card, which will allow your H1B to be renewed indefinitely, but you still have the alien conditions including needing to maintain the same/similar employment.