It's hard to convey to a citizen how demoralizing being on an H1B is. If you get laid off, you have at best 30 days to find a new job and transfer your visa (from what I remember), otherwise you have to leave the country. H1B does not allow moonlighting. You can't start a startup by yourself. You can't take significant time off between jobs unless you transfer your visa and negotiate it. Your spouse likely won't be able to work (it's not trivial). You can't protest unfair working conditions to the extent a citizen can, because getting fired is effectively exile. Calling it indentured servitude is accurate.

I'm sure most people understand that it's a transactional relationship, I.e. you get to live in the country while you work and that's it, but if you live in a city for several years and settle in, form friendships, hobbies, and maybe relationships, it's very difficult to put all of that at risk for any reason.