Why does there need to be more housing built in an already dense area? People have moved for thousands of years to areas where they were more easily able to af

Why does there need to be more housing built in an already dense area? People have moved for thousands of years to areas where they were more easily able to afford to buy or build a home. My parents moved from basically a 3rd world country to the US, not speaking the language, with about $200 in 1988. They already had me as a child to deal with too. Now a college grad doesn't want to move to another part of the US to afford a cheap house?