[frmersdog]

And the jobs? The amenities that make areas highly desirable require workers who can actually commute to them.

It's a game of chicken. The people who live in these areas and expect to be served without complaint either acquiesce to density and lower property values, or risk (occasionally fiery) demonstrations against the unfair and unworkable situation. Their goal is to keep the game running, so that everyone else doesn't decide on one or the other end state. Essentially, "Highly desirable areas that are too expensive for low/middle-income workers," is a transition state.