Dense urban areas provide excellent opportunity for rent seeking by urban land owners. The mobility provided the automobile (also rail and bicycles) made it practical to live outside urban areas where land is cheaper, which also permitted lower density. Urban land rent decreased significantly between the late 19th century and the mid 20th century.

The alternate future would have seen everyone living in dense urban areas paying most of their wages as rent to the descendants of gilded age land owners.

edit: spelling