Why Shouldn't the 14th Amendment protect homeowners in HOAs?

While the following Supreme Court decision focused on a Midland County's (TX) apportionment of voting districts, the reasoning applies to any local government.

With respect to HOAs, why does state government allow a devise of a questionable "informed consent" private contract to permit developers to circumvent the law as applied to local governments? Could it be that the enforcement of a coercive contract is necessary in order to obtain the compliance to the authoritarian planned community HOA government, on a nation that prides itself as the champion of individual rights and freedoms?

Excerpts from AVERY v. MIDLAND COUNTY, 390 U.S. 474 (1968)

The Equal Protection Clause does not, of course, require that the State never distinguish between citizens, but only that the distinctions that are made not be arbitrary or invidious.

Thus the prohibitions of the Fourteenth Amendment extend to all action of the State denying [390 U.S. 474, 480] equal protection of the laws; whatever the agency of the State taking the action . . . ." Cooper v. Aaron, 358 U.S. 1, 17 (1958) . . . . The actions of local government are the actions of the State. A city, town, or county may no more deny the equal protection of the laws than it may abridge freedom of speech, establish an official religion, arrest without probable cause, or deny due process of law.

[Now, follow this argument]

That the state legislature may itself be properly apportioned does not exempt subdivisions from the Fourteenth Amendment. While state legislatures exercise extensive power over their constituents and over the various units of local government, the States universally leave much policy and decisionmaking
to their governmental subdivisions. Legislators enact many laws but do not attempt to reach those countless matters of local concern necessarily left wholly or partly to those who govern at the local level.

What is more, in providing for the governments of their cities, counties, towns, and districts, the States characteristically provide for representative government - for decisionmaking at the local level by representatives elected by the people. And, not infrequently, the delegation of power to local units is contained in constitutional provisions for local home rule which are immune from legislative interference. In a word, institutions of local government have always been a major aspect of our system, and their responsible and responsive operation is today of increasing importance to the quality of life of more and more of our citizens.

We therefore see little difference, in terms of the application of the Equal Protection Clause and of the principles of Reynolds v. Sims, between the exercise of state power through legislatures and its exercise by elected officials in the cities, towns, and counties. 6 [390 U.S. 474, 482]

We will not bar what Professor Wood has called "the emergence of a new ideology and structure of public bodies, equipped with new capacities and motivations . . . ." R. Wood, 1400 Governments, at 175 (1961). Our decision today is only that the Constitution imposes one ground rule for the development of arrangements of local government . . . .