Why do people say “just don’t live there” or “move then” when people complain about the cost of living in their area?

How are you supposed to move hundreds of miles away potentially when you're broke? Why should people have to leave all of their friends and family and the only place they've ever known? Who would work there then? I'm thinking of LA County specifically. Ok, let's say everyone who doesn't make like $35 an hour (basically what it takes to scrape by in LA County) moves. Who's going to provide services? No restaurants or retail of any kind or cleaners or childcare workers. They all moved to another state. Sorry.