My speculation is that they are giving preference to countries where the people are easier to exploit, an upgrade in lifestyle being here at any pay and a cultural obedience to hierarchy and business.
To a point, yeah. But at the same time, for this sort of
labor arbitrage to work, you still need the skillsets and training. India and China are of interest right now in particular because they are both growing economies, have a growing middle class, and a culture that is pushing a
lot of people to get highly educated. The problem is that India in particular faces a wealth gap worse than the US, rampant corruption in their institutions, which creates both a glut of educated labor that their own economy can't leverage, and an environment where if you are able to build wealth, you either need to get used to greasing palms or get the heck out of dodge. China, while it's doing better at absorbing the talent, is still a one-party state with corruption issues which will create a push for emigration for many people who are educated, but run the risk of running afoul of the party. And in many cases, taking the H1B offer means better pay than they would get at home, and the chance for permanent resident status under more tolerable living conditions.
So yeah, there's plenty of people that will accept this sort trade. Damned if you do, damned if you don't.
It's my experience that they have a high work ethic, and will take any amount of shit a terrible company owner/sponsor can throw at them. If you'll recall back when Musk took over Twitter and expected people to essentially live at the office and work 20 hours per day, engineers were telling him to go fuck himself, H1B is in no position to say no. This is why those who exploit the most want them want them, filthy billionaire assholes who couldn't care less about you, your family, or your livelihood as a human being.
From the perspective of the H1B worker, they are here at the mercy of their sponsor, so what
are they going to do? Here's the thing, if I thought keeping my head down would let me get my green card, stop being an H1B and then be free to look for another job? I'd probably keep my head down.