There’s a limit on number of green cards per year. Then there’s a hard limit of 7% of that per country. There’s also a priority system with Family coming first. The combination of three results in a really long wait time for Indians without family (who are citizens) in the US moving on H1B. The current priority date is 2012 if I’m not wrong. It did progress faster during the pandemic but got quickly rolled back. Remember that those who come on H1B are already capped per year.

https://travel.state.gov/content/travel/en/legal/visa-law0/v...