I am surprised you think that uprooting your entire living and moving to a different country is that easy: I mean do you do that for convenience sake even inside the USA?
These are people (including me) who come in here and build a bunch of local connections. Turning it personal, Our kids go to school here. I own a house here. I have a ton of friends here. I pay taxes and donate/volunteer when I can. I ride bicycles everywhere if that matters. (No I am not blue/democrat because I can't vote :).
You are also touching on other issues like visa hostages. Most of those people who feel that they are in a 'hostage' scenario can go back anytime they want but most of them choose to stay. I say most because there are definitely a few who can't but whatever.
In my case, I could've stayed back in India and worked for similar companies (Both my prior companies have a big presence there), but here is where I want to be. Now you can say me being here ONLY benefits my employer or elites, but I definitely don't think of that way: I think of it as an incredible opportunity and like any other big-system process, it has its troubles. ¯\_(ツ)_/¯