It isn't a failing of the free market. It's a failing of zoning regulations which are decidedly not a free market institution. Developers would be happy to be

It isn't a failing of the free market. It's a failing of zoning regulations which are decidedly not a free market institution. Developers would be happy to be build more walkable communities but zoning regulations like minimum setback, minimum lot size, parking requirements and the rest force them to build low density suburb neighborhoods. People choose the government they get (generally), and many people have a NIMBY attitude towards increased density, thus they seek out such communities.