It's easy to say move, but much harder to actually do it. A lot of people flat out cannot afford to move half-way across the country, period, full stop, nor can they afford the added risk of getting new jobs. Plus, odds are good their salary where they're moving to is less, so it's not clear that they'll easily now be able to survive on a single salary anyway.
Plus, this solution isn't highly scalable; only so many people can do it.