HOAs have a lot of applications that aren't horrible, you just probably dont hear about them. Neighborhoods with HOAs are often centrally planned, so there will be common areas that require upkeep like pools, clubhouses, parks, etc. They essentially take on a form of government role. In a lot of neighborhoods that are not part of an incorporated city, they do things like trash collection, road upkeep, snow plowing, etc.
I've lived in 2 places with an HOA, and in the one, all they did was the landscaping, even around all the yards of the houses. In the other, they handled the park/pool/clubhouse, and they did trash collection.
The down sides are often because the people in charge are just retirees who hunger for power, and there isnt much oversight from real government. Most people dont care enough to try to oust the bad leaders, so they stay in control, and they often do things that are illegal, but no one calls them out on it.