Moving is expensive as well. When you hear about families being unable to buy diapers in bulk because they can't save the $50 needed for that and instead buy smaller quantities at twice the cost per diaper you realize that some people simply can't afford to move somewhere cheaper as crazy as that sounds.
Yeah but with UBI everyone would suddenly have a great source of credit. Who wouldn't loan someone $10k to move at a low interest rate when you know that person by being a US Citizen is receiving $10k/yr.