short answer: there's a misguided perception that a small patch of grass makes a house more valuable

long answer: HOAs are an illusion of self governance. in reality they serve banks and have become a common feature of nearly all housing developments. the banks originally acquired the land via violent means, declaring it their own despite the land already having residents in the form of indigenous people. it was then the banks who funded the violent enslavement of Africans and their trafficking accross the globe into the African Diaspora. the banks exist to serve white supremacy. they have done this in a variety of ways through the centuries. these are not all the ways:

1. creating a split deed between the surface rights and mineral rights
2. enforcement of structures of poverty through coagulating wealth
3. entering contracts with slavers demanding perpetual enslavement of trafficked humans
4. sponsoring segregationist policies
5. redlining (not approving loans for minority homes and business purchases in certain parts of a city)
6. the creation of HOAs to enforce white upper middle class ideals on lower middle class and working poor families