The HOA provides the regulations and guidelines for the community. These standards are actions that must or should be done with the aim of preserving and enhancing the community’s property values. Often, they are appearance-oriented, dealing with cleanliness, condition, and repair. Sometimes they are designed to keep a uniform appearance to the included properties or the community as a whole.
On a more theoretical level, HOAs are symbols of self-governance and democracy. Who better to run a community than the people living in it—as opposed to some absentee landlord?