Every H1B I know is both underpaid and unable to change jobs. The companies that use them the most are those that squeeze their employees the hardest. They work hard and are incredibly smart and capable, but they have no power to push back on the boss asks them to come in on nights and weekends.
It’s a fiction, like the idea that contractors would prefer contracts over full time employment. Its a less-privileged workforce with fewer protections to benefit the companies.
I’m pro immigration, and that means actually paying people for their expertise rather than semi-indentured workers. Too often companies get all the benefits of the workers without having to pay them. The fact of all the staffing agencies put in alongside Microsoft. Of course, the current admin couldn’t care less about any employee, citizen or migrant, they’re just using it to try to show their base they care. The dems have done absolutely nothing when they are in power either.
There are exceptions, but in 20 years in both SF and Seattle you can basically set your clock to this being what’s happening.